391

EASTER FIELD MEETING, 1933.TENBY AND THE SOUTH PEMBROKESHIRE

COAST.

REPORT BY THE DIRECTORS; THE PRESIDENT AND E. E. L.DIXON, B.Sc., F.G.S.[Received lsi November, 1933.]

THE party assembled at Tenby on the evening of Thursday,April rjth, headquarters being, as on the occasion of the formervisit in 1909, at the Cobourg Hotel. About forty membersattended and these, with a few friends and local visitors, made atotal of nearly fifty who attended during some or all of theseries of excursions. Miss G. M. Bauer acted as Secretary forthe Meeting.

Friday, April 14th.

Freshwater East, Swanlake and Manorbier.

Leaving Tenby at 9.15 a.m., the party drove along theRidgeway to the highest point (about 350 ft. O.D.) where, besideNorchard Beacon barrow, the Directors drew attention to thelandscape features and their relation to the 'solid' geology ofthe district. Continuing thence to Lamphey the party crossedthe Pembroke syncline to Freshwater East, where the relationof the valley which here opens to the sea to the denuded Fresh­water East anticline was indicated. No exposures of the Ordo­vician shales, which outcrop in the valley, could be examined,but fossiliferous horizons were accessible in the Silurian (WenlockBeds-poorly seen and without distinctive fossils-and LudlowBeds) below the basement-conglomerates of the Old Red Sand­stone (Downtonian) in the southern cliffs of the bay. The partystudied the outcrops of the Ludlow Beds and Downtonian(A uchenaspis Group) also in the cliffs on the northern side of thebay, and here Prof. W. H. Lang gave an account of his work onthe fossil plants in the local Old Red Sandstone. A fine cephalas­pid fish which he had found in the A uchenaspis Group andgenerously presented to Jermyn Street Museum-the mostcomplete specimen of an Old Red fish known from Pembrokeshire,as some of the body-segments were preserved-was identifiedby Sir Arthur Smith Woodward as a Hemicyclaspis of theMurchisoni group.

The beautiful cliffs that extend from Freshwater East toOld Castle Head display the vertical beds in the northern limbof the Freshwater East anticline. Coastal profiles include theelements of (1) plateau, (2) scarp bevelled off along the cleavagewith an almost uniform southerly slope of about 30 degrees,(3) shore-platform of recent marine erosion, (4)sea-cliff at the headof this platform. On this occasion, when bright sunlight brought

392 THE PRESIDENT AND E. E. L. DIXOK,

out all the varied colours of the rocks, the scenery of the cliffswas admirably displayed. The party next drove to East Moorand walked down to Swanlake Bay, where some of the membersexamined the Psammosteus Limestone Group (conspicuous byreason of its coarsely-nodular limestone) in the eastern cliffs forplant- and fish-remains; while others traversed the rough fore­shore to the exposure of red marl which contains numerous andwell-preserved fish-remains (Dittonian). The beds in thishay display also, admirably, the fossil ripple-marks and sun­cracks which form part of the evidence for the view that sedi­mentation took place under "continental" conditions. Re­joining the coaches, the party drove to Manorbier and examinedmarls, sandstones and limestones in the eastern cliffs of the bay,where Psammosteus and other fish-remains, Pachytheca and lowlyplants were found in sandstones and shales of the PsammosteusLimestone.

The cliffs on each side of Manorbier Bay show many interest­ing results of differential erosion in deep vertical grooves andtrenches locally called" fissures," which are spaces left by theremoval of beds of shale and of marl from between hard sand­stones. The coastal profiles are those which enter into the generalview of the cliffs obtained from Freshwater East, but the shorerock-platform, cut across the edges of vertical beds, is exten­sively developed on the western side of the bay and merges intoremnants of the pre-Raised Beach platform above the presentbeach.

After tea at J\Ianorbier the party drove back by way of Lyd­step, Penally and across the St. Florence syncline to Tenby.

Saturday, April 15th.Old Castle Head, Skrinkle Haven, Lydstep Head.

The party left Tenby by coaches at 9.15, drove to SkrinkleFarm and walked out to the cliffs at Cunigar Pit, where Mr. Dixongave an account of recent work done on rocks which havehitherto been grouped as Old Red Sandstone, but which, onaccount of Mr. W. Wickham King's discoveries of marine lamelli­branchs and his investigation of the fish-faunas, may possibly infuture be referred to the Silurian (see pp. 217 and 402). Thethinly bedded sandstones (Cephalaspis Sandstones) at this pointyielded several rostra and fragmentary shields that were identifiedby Sir Arthur Smith Woodward as Pteraspis crouchi Lank.

The party then proceeded to Old Castle Head, which of allpoints along this coast exhibits most remarkably the gullies,grooves, ribs, trenches, etc., which arise from the differentialerosion along bands of tectonic or lithological weakness. Theperfect weather conditions permitted the members to examineevery part of this headland. A few who clambered down the

EASTER FIELD MEETING-TE:\BY AND S. PEMBROKESHIRE. 393

cliff-face into Sandy Hole secured good specimens of Pacbytheca.On the party proceeding to Skrinkle Haven attention wasdirected to the Ridgeway Conglomerate, the Skrinkle Sandstones(Upper Old Red Sandstone), which here contain one thin marine(Devonian) intercalation, the fossiliferous shales at the base of theAvonian, and the shales and limestones of the lower part of theCleisiopora zone.

After lunch the tide had fallen sufficiently low to permit somemembers of the party to enter the inner cove beyond the ChurchDoors limestone. Several good specimens of "Cleistopora '(Vaughania uetus L. B. Smyth) were collected and the sequencewas examined from K2 to the chert beds in the Lower Zaphrentiszone, but the height of the tide did not permit the members topass through Skrinkle Arch into the innermost cove where thefossiliferous higher beds of this zone are exposed. LeavingSkrinkle Haven somewhat unwillingly the party walked to a fineview-point immediately east of the inlet, and here the generalrelations of the coast features to the geological structure weredemonstrated. The groups of relatively strong and weak beds,developed into promontories and coves in the Old Red Sandstonecoast and into saddle and peak features on the CarboniferousLimestone; gash-breccias; ancient solution cavities enlargedinto sea caves; and the plateau-like surface of the CarboniferousLimestone in both limbs of the Pembroke-Lydstep-Giltar Pointsyncline, were all easily discernible. Proceeding past SkomerSaddle (enclosed by a small cliff-castle) the party reached thedry valley which runs down to the shore at Lydstep Caverns.Gash-breccias with interstitial red stalagmitic marls are welldisplayed in the cliffs of the gorge. Near the head of the beachlies a large norite boulder, probably a glacially transported erraticfrom the region about St. David's Head. The height of thetide did not permit the western caves to be examined, butmost of the party made their way into the great Smuggler'sCave and emerged from the wide vertical shaft which opens uponthe hillside from the inner end of this cave.

Lydstep Head, between the Caverns inlet and Lydstep Bay,presents many features of great interest to which, however,only a short time could be given.

The whole headland exemplifies the plateau-forming tendencyof the surface of the Carboniferous Limestone, but the generallevel is distinctly trenched by a series of incipient saddles erodedalong thin beds at the base of the Seminula zone. At BlackMixen (C1--Canillia Oolite-and C2 sub-zones) occurs an exposureof Raised Beach under firmly cemented head, or rubble-drift,and near Whitesheet Rock there is a fine example of the RaisedBeach rock-platform, backed by contemporary cliffs all cut ina remarkable mass of gash-breccia which (particularly at thewestern end of the platform) exemplifies the mode of origin of

394 THE PRESIDENT AND E. E. L. DIXON,

these breccias by the collapse of large caverns. Time did notpermit any lengthy examination of the Visean (S- and D-zones)of the headland nor of the chert-debris, including radiolariancherts from near the base of the Millstone Grit, probably theEumorphoceras zone, in an old mine-tip opposite Lydstep Lodge.After tea at Lydstep the party rejoined the coaches and droveback to Tenby.

In the evening, after dinner at the Cobourg Hotel, Sir ArthurSmith Woodward very kindly gave an address upon the relationof some of the more primitive fishes (lampreys and hag-fishes)of the present day to the Ostracoderm fishes of the Silurianand Old Red Sandstone formations. This address, which sum­marised recent advances in the study of fishes, was very greatlyappreciated by the members as a lucid exposition of problemsconnected with the evolution of modern fishes.

Sunday, April 16th.Amroth and Saundersfoot.

Soon after 9 a.m. a large party of the members made a tourof the more interesting parts of the mediaeval Walls, which werebuilt while the Norman conquest of South Pembrokeshire wasbeing consolidated and which still remain in excellent preserva­tion on the landward side of the town.

At 10 a.m. the party left by coach for Amroth, where, thetide being high, attention was first directed to the gaps madein the coast-road by recent storms and to the great shingle­beach heaped across the mouths of the valleys on each side ofAmroth. The western stream passes through the shingle bymeans of a culvert, but the eastern stream, which has no openoutlet, percolates through the shingle below New Inn. At BlackHall Point some old workings for coal, opened in the face of thecliff, enabled the party to examine a thin seam underlain byfire-clay containing abundant ironstones. Returning to thewestern end of Amroth, the party began to study the remarkablecliffs of Coal Measures in this most highly disturbed part ofthe coalfield. The section prepared by the Geological Surveyfor the Haverfordwest Memoir had been reproduced in thepamphlet issued in advance of the Field Meeting, and all thestructures shown therein could be identified with ease.

At the point where the disturbances become most pronounced,Dr. Emily Dix, F.G.S., gave a brief address upon the difficultiesinvolved in any detailed classification of the strata usually termedMillstone Grit and Coal Measures. The beds between Amrothand Saundersfoot belong to Middle Coal Measures (Yorkian).Good collections were made of plant-remains and of lamelli­branchs : Carbonicola occurs very abundantly in a light-colouredbed which forms a prominent feature in an anticline west of

EASTER FIELD MEETING-TENBY AND S. PEMBROKESHIRE. 395

Amroth. The whole range of cliffs presents numerous interestingstructural features, one of the most striking being an S-shapedfold in massive sandstones, broken in the middle limb, andpassing into an overthrust fault.

Beyond 'Wiseman's Bridge the party continued by the mineralrailway which runs along the foot of the cliff and passes throughthe pitching anticline under Hean Castle. This fold is cut by twoplanes approximately at right angles: (r) the shore-platform,(2) the cliff-face: on each of these surfaces hard sandstones formprojections between curving grooves eroded along shales andcoal-seams. From the next headland the party walked along thebeach past Saundersfoot harbour to examine the steeply-foldedanticline below St. Bride's; then, as neither time nor the stateof the tide permitted a visit to be made to the buckled anticlineat Monkstone, the party returned to Saundersfoot for tea anrldrove thence into Tenby.--(A. L. L.)

Monday, April 17th.North Shore, Tenby and Giltar Cliffs.

The party walked to First Point, where Mr. Dixon demon­strated the synclinal structure in which the Farewell Rock andthe underlying ripple-marked shales are involved in this headland.The shales and sandstones between First Point and Tenby aregreatly disturbed by folds and faults. A bed of shale in thecliff near Middle Rock yielded several goniatites and marinelamellibranchs which may prove to be of value in determiningthe stratigraphical position of these strata (see pp. 409-II).

Continuing along the beach past the brecciated limestonesexposed in Barrel-post Rock on a branch of the Ritec overthrustfault, the party reached the group of black shales with limestonebullions, between this rock and Tenby harbour, where in rgo9Dr. Wheelton Hind collected fossils which led him to regard thesebeds as representatives of the Pendleside Series. The beds arcnow known to belong to the Homoceras zone (Chokier horizon).

In the afternoon the party set out across the Burrows towardsGiltar Point, where the zonal sequence in the cliffs in the north­eastern cliffs of this headland ranges from C, (Cal1il1ia Oolite) toD1 , the main exposures being in Seminula oolites. The smallkitchen-middens amidst the sand-dunes on the summit of theheadland were well exposed and several fragments of crudeEarly Iron Age pottery were found. The date of these middenscannot be exactlv ascertained.

From the Point, the members walked westward along thecliff-top noting several very fossiliferous horizons and also thegash-breccias, solution-cavities, blow-holes and cauldrons whichoccur abundantly in the massive beds of the Seminula zone.Near Valleyfield Top a cliff-section exposes limestones, undis-

l'ROC. GEOL. Assoc., VOL. XLIV., PART 4, 1933. 26

396 THE PRESIDENT AND E. E. L. DIXON,

turbed except for their steady dip, overhanging gash-breccia.Having reached Proud Giltar, an excellent view-point for theRidgeway, the Pembroke syncline and the coast westward toOld Castle Head, the party turned inland to a quarry in ZI lime­stones near the Barracks and continued thence by road to Penallyvillage for tea, returning to Tenby by train.

In the evening, Mr. W. S. Bisat, F.G.S., who had spent thegreater part of the day in First Bay and on the cliffs betweenFirst Point and Tenby, exhibited some of the goniatites whichhe had collected, together with those obtained by other membersof the party during the morning, and briefly discussed theirbearing on the classification of the highly-disturbed beds imme­diately north of Tenby.

Tuesday, April 18th.Freshwater West, Linney Head and Stack Rocks.

The party left Tenby at 9.15, drove along the Ridgeway toPembroke, halting there to examine the more interesting partsof the Castle including the Wogan Cavern, and then went on toBulliber near Castlemartin where they left the coaches andwalked down to the shore of Freshwater West near the mouthof Frainslake brook. The Lower Avonian (Tournaisian) lime­stones here exposed in the southern limb of the CastlemartinCorse anticline (a member of the Orielton compound anticline)afford excellent exposures of highly fossiliferous beds (Z2 andHorizon r). the most productive portions of the section beingin the cliffs above Bluckspool. A long fish-spine found here byDr. Dix has been identified by Prof. Watson as similar to thosecalled Physonemus. To the east of Bluckspool the ground risesto the level of the plateau-like limestone-flat, which extends toStackpole Head at a fairly uniform level. The cliffs south ofBluckspool and thence to Berry Slade are made up of massivewhite dolomite, part of a dolomite-reef, some hundreds of feetthick, of CI age and, therefore, correlative with the Waulsortianreefs of Belgium. Near Berry Slade the highest dolomites passlaterally into well-bedded dark limestones and dolomites ofstandard type. Near Hanging Tar, where the cliff is accessiblewith care, the succeeding thin-bedded dark limestones and chertsin the lower part of C2 enclose a great lenticle of thick-beddedpale reef-limestone devoid of chert. When deposited, this wasclearly a fairly sharp, local elevation on the Carboniferous sea­bottom. The thin-bedded dark limestones into which the' reef'passes laterally yield an abundant zaphrentid-phase fauna; the

reef' is almost unfossiliferous except for fenestellid bryozoa andcrinoid-debris. It is, in fact, a bryozoan-reef.

Both from the tectonic and from the lithological points ofview these cliffs present scenes of great interest. Chert is present

EASTER FIELD MEETING-TENBY AND S. PEMBROKESHIRE. 397

in enormous quantities, in regular layers of nodules in the thinly­bedded limestones, and some of the nodules exhibit curious con­centric structures which suggest silicified organisms. TowardsPen-y-holt Bay many folds in the cliffs assume a text-book likeclearness and symmetry. The buckled anticline which formerlycontained the Cabin Door arch was destroyed several years ago;it was, however, noted that the sea had swept away all theenormous mass of limestone blocks which must have fallen to theshore when this arch collapsed.

In this southern district, where no Caninia oolite has been re­cognised, the highly fossiliferous mudstones and limestonesexposed in the cliffs of Mount Sion Down form an undivided seriesof Upper Syringothyris and Lower Seminula beds (C.-S,). Hereand there along the cliff-top, and particularly just west of TheWash, there lie small patches of white quartz gravel, remnantspossibly of a Pliocene superficial deposit of fluviatile origin.

At numerous points the controlling influence of geologicalstructures upon erosional features is admirably displayed andmore especially at such oft-visited scenes as The Wash, StackRocks, Green Bridge arch and The Cauldron near Flimston.It was pointed out that the beds in these cliffs, lying west ofFlimston Bay, had a gentle northerly dip, whereas at Crocksydamand Bullslaughter Bay, along the same strike, but east of Flim­ston Bay, the cliffs displayed a steep, buckled syncline (examinedat close quarters on the following Thursday). The explanation isthat the great Flimston Bay cross-fault, which separates the tworanges of cliffs, effects a huge lateral displacement or ' heave'of the axis of the Bullslaughter Bay syncline. West of the faultthe continuation of the axis lies about half-a-mile out of lineto the north-west; the northerly-dipping beds so well displayed atThe Wash belong to the southern limb of the syncline at a con­siderable distance from the axis.

After tea at Flimston, two points of interest were visited, viz.,old pits in pipe-clay (? Aquitanian), where formerly this materialwas manufactured into bricks, and also the group of large erraticboulders gathered from the surrounding district, and placed forsafety in the enclosure surrounding Flimston Chapel by the lateLt.-Col. F. W. Lambton. Two of the largest of these bouldersstand as headstones to the graves of Col. Lambton and of his wife,Lady Victoria Lambton. At Flimston the party rejoined themotor-coaches and drove back through Merrion, Monkton andPembroke to Tenby.

Wednesday, April 19th.Tenby (South Cliffs) and Vicinity.

Leaving the hotel at 9.15 the party walked to Castle Hill, anexcellent view-point for the prospect across the great syncline

THE PRESIDENT AND E. E. L. DIXON,

in Upper Carboniferous rocks between Tenby and RagwenPoint. From this position also the effects of the Ritec faultsupon the rock-outcrops east and north of Tenby can be demon­strated. The zonal sequence in the limestones of the Castle Hillranges from Upper Zaphrentis-beds with abundant chert nodulesin the northern cliffs to brecciated Laminosa-dolomites above theSouth Beach.

The party next visited the local museum housed in a buildingwhich incorporates some remnants of the walls of the ancientCastle. In the forecourt three erratic boulders of norite fromthe region about St. David's Head are preserved. Two ofthese were found recently in excavations in Heywood Laneand Maudlins Road respectively: the third was brought in fromSlade near Manorbier.

The anticline, which is exposed in the cliffs above the SouthSands, can be minutely examined from the beach. The sequencefrom S1 to C1 in the north limb and the ascending sequence C1to S2 in the south limb has been fully described in the Memoirand in the Report of the Excursion to Tenby in 1909. On thisoccasion the beds in each limb were examined as far as theProducttts-bed, in S2' in Rack (or Wreck) Field quarry.

After an interval for lunch the party walked along HeywoodLane to Gumfreston Church, one of the most interesting inSouth Pembrokeshire. Chalybeate springs which issue in thelower part of the churchyard were long ago, possibly in medirevaltimes, enclosed in masonry basins, but they are not now visitedfor the medical qualities of the waters. They come out nearthe junction of the Lower and Upper Carboniferous rocks, anda small exposure of limestone near the church has yielded fossilsindicative of a high zone of the Main Limestone. From Gum­freston the party walked to Upper Nab Bridge, and after visitinga large glacial erratic which lies on the edge of a disused quarry,and is now almost obscured by an overgrowth of brambles, theycrossed the marsh to Holloway where a norite boulder now standsas a gate-post. From this point they proceeded to Hoyle'sMouth or The Hoyle cave which has yielded certain flint andadinole implements of Late Palseolithic forms, and continued toLongbury Bank cave where was obtained the large collection ofpost-Paleeolithic relics now preserved in the Tenby Museum.The origin of these caves as channels for drainage from a land­surface which existed before present valleys came into existencewas briefly discussed. From this point the members of the partywalked into Penally, returning to Tenby by train.-(A. L. L.)

Thursday, April 20th.St. Govan's Head to Stack Rocks.

The programme for the day included the examination of thatpart of the southern limestone plateau which extends from St.

EASTER FIELD MEETING-TENBY AND S. PEMBROKESHIRE. 399

Govan's Head to Flimston. Leaving Tenby at 9.I5 the partydrove through Gumfreston and Carew, Pembroke and Bosherstonto St. Govan's Chapel. The cliffs of massive limestone (Dibuno­phyllum zone) show the controlling influence of the joints uponthe forms of the cliff profiles. The party walked out to theextremity of the headland, where a large erratic boulder (prob­ably from a locality in North Wales) lies on the edge of the cliff,and then returned to the chapel where at the marl-pit near thetop of the gully Mr. Dixon gave an account of his reasons forconsidering these reddish clays as deposits of New Red Sand­stone age. The chapel stands athwart a gully eroded along afault-plane, and the adjacent cliffs display good sections inpseudo-breccias and other limestones of the Dibunophyllumzone (D,).

From this point the party walked westward along the almostlevel coastal plateau noting at Stennis Ford, Huntsman's Leap,Bosherston Mere, Crocksydam, etc., many striking features ofcliff scenery in which the results of the interplay of structure anddenudation could be traced. The small cliff castles at BuckspoolDown and on Moody Nose added some archseological interest tothis traverse. At Bullslaughter Bay and Crocksydam, a positionof great stratigraphical interest, fine exposures of the gash­breccias and of the highest beds of the Dibunophyllum zone(top of Dr and D,) were examined. These beds lie in the steepbuckled Bullslaughter Bay syncline, which was seen from thewest side of Flimston Bay on the previous Tuesday. AtCrocksydam the earth-pressure has sheared intensely theDj-Iimestcne along the junction with D,. Two beds of oolitein D, are of interest in that their fauna differs from that of therest of Ds, which is that of a zaphrentid-phase. In both ofthese oolites fine specimens of oolitic chert have been found,but during the present visit only a few poor examples wereobtained.

In the cliffs of Flimston Bay, between Bullslaughter Bay andStack Rocks, other fine examples of gash-breccia are displayed,and some of these have been further broken up or almost pul­verised by movement along the great cross-fault (mentioned onTuesday) that displaces the westward continuation of the Bull­slaughtcr Bay syncline.

The party, having now reached a position which linked theday's traverse with that of Tuesday, had completed the examina­tion of the whole of the southern plateau between StackpoleHead and Freshwater West. After tea again at Flimston thosewho had not seen the erratic boulders and the pipe-clay wereable to visit them on this occasion. The party then drove backto Tenby.

400 THE PRESIDENT AND E. E. L. DIXON,

Friday, April 21st.

Freshwater West and West Angle Bay.On this, the last day, the work to be done lay in the western­

most part of the South Pembrokeshire peninsula, beyond theground examined on the roth. Leaving Tenby at 9.15 a.m, theparty drove through Pembroke to Freshwater West. CorstonBeacon, a Bronze Age tumulus, was seen, en route, and atKilpaison Burrows (sand-dunes), a fine dolmen called the Devil'sQuoit. At Freshwater West attention was confined to the neigh­bourhood of Little Furzenip, in order to compare the sequencewith that between Freshwater East and Skrinkle Haven (April14-15).

To the north the Neolithic Submerged Forest, the BifidusShales, the Ludlow Series and the lowest Downtonian are tobe seen only on the foreshore, and exposures depend on tide andthe extent of shore-sand. The' Forest' was found to be fairlvwell exposed; also the Bifidus Beds, overlain immediately by theLudlow Series, but the soft disturbed state of the former pre­cluded successful fossil-hunting. The Ludlow Beds were seento be chiefly fine breccias and beds with plant fragments (of whichsome were taken by Professor Lang for examination). Theirthinness and the absence of the thick series of sandstones presenton the south side of Freshwater East are to be ascribed to theunconformity at the base of the overlying Downtonian (seep. 40 2 ) .

As at Freshwater East, the latter commences with con­glomerates, and apart from the absence of the A uchenaspisGroup, the rest of the Downtonian-Dittonian sequence can befairly well distinguished. But at Freshwater West, above thebasal conglomerate group, which is much thicker, the groups,individually and collectively, are much thinner, and no coarselynodular limestone is developed in the Psammosteus Limestone.The latter was recognised by means of its abundant fish-frag­ments, among which a specimen of Anglaspis was found. Thelimestone is exposed along the northern edge of Little Furzenip,where sandstones become prevalent as the series is ascended.Time did not permit a search for the Cephalaspis Sandstones.The Dittonian was noticeably thin. In support of WickhamKing's suggestion that the overlying Ridgeway Conglomeratemay be unconformable, it was observed that the Dittonianbelow the lowest conglomerate, bared clean on the foreshore, waseroded and uneven. The question, however, is not settledthereby, as contemporaneous erosion has almost universallypreceded the deposition of each sandstone in the ' Old Red.'

The exotic appearance of the Conglomerates, interbeddedas they are chiefly with fine-grained red marls, was noticed;also the great development of Skrinkle Sandstones (Upper Old

EASTER FIELD MEETING-TENBY AND S. PEMBROKESHIRE. 401

Red Sandstone}. The party then returned to KilpaisonBurrows,and thence went on through Angle to West Angle Bay, wherethe feature of importance was the presence of marine UpperDevonian bands intercalated in the upper part of the Upper OldRed. These bands are best developed on the south side ofthe bay. The tide prevented their being reached along theforeshore, but, after a scramble, the cove (' Third South Cove ')that displays them in sequence with Km, the Modiola-phase at thebase of the Lower Limestone Shales, was gained. Here a typicalblack limestone with Phychopteria damnoniensis was the lowestmarine band accessible at the time; its base penetrates the topof the underlying mudstone irregularly, as though along boringsor cracks.

In the middle of the cove a half-tide rock affords the bestexposure in Pembrokeshire of the red sandy Bryozoan Lime­stone (cc-typc) in Km. A fine-grained oolite and various otherbeds between this horizon and the Old Red Sandstone may beparalleled exactly at Skrinkle Haven.

The north side was then visited, where a grey bed with coalylaminre is intercalated in the Upper Devonian, but it was putout of reach by the tide.

After passing back along the Lower Limestone Shales-which,more noticeably here than elsewhere in Wales, have been wellcleaved by the Armorican earth-pressure-the CarboniferousLimestone (Z,) in the middle of the bay was examined. Here theparty was fascinated by a colony, covering several square feet,crowded with complete examples of sea-urchins (Palechinus)and crinoids with arms and pinnules attached. Elsewhere in thePembrokeshire Carboniferous even isolated sea-urchins or crinoidswith pinnules are almost unknown. The colony well illustratesthe imperfection of the average geological record. Incidentallythe colony has been repeatedly trodden on for many years, butseems to have suffered little since it was first noticed in 1912.

After a short visit to the old brick-pit, which formerly showedexposures of gravels, loams and clays, with glacial erratics andplant-fragments, tea brought the Easter Field Meeting to a close.

(E.E.L.D.).