ON THE PRE-CAMBRIAN ROCKS OF PEMBROKESHIRE. 507 
37. On the Pre-Camprian Rocks of PemBRoKusHiRE, with especial 
reference to the Sr. Davin’s District. By Henry Hicks, M.D., 
F.G.S. With an Appenpix by Tuomas Davizs, Esq., F.G.S., of 
the British Museum. (Read May 14, 1884.) 
[Puate XXTV.| 
ConTEnTs. 
PAGE 
REPRE ATOOCMING CEOTU bi Me aah aoe ce circ caryarrieraicele seniciate Nerestesls ice alia nite da's deion devine 507 
II. Corrections suggested in Maps of the Geological Survey ......... .. 509 
Mier Goikie’s CONCLUSIONS (2.2 .2..-..2scccescccsetmasmss seve ciecececteseoeers 510 
TV. Main differences between our viewS............. Bie Mase oneeeeetascetcicns 510 
We biaMametian Rotks: ich eetttes veseswecd LotR ret SO os batiahda 511 
GREP ENEO OLAS! fs ropeciasimaacpmethwtdun tay vob pollnotaden Nasties Mees saisob tic 511 
PemiveweAreas Im Pembrokeshire: . «2s04uie sacsae ajar neces cis aciosinetes seins ‘512 
OME OH DV IMTELIAN FLOCKS) 1... 0000002 sesseaucwesiecsmecesersossssnases 513 
PeBMMeMNECCCIAtCd FOLtlONS «... .0262...-cncecacecsduscatavensacceasiac actlsles 513 
e. Petrological Characters ................ a fa betn alah Seecticeteeeicanen das 514 
VI. The Arvonian Rocks ..............0. pad te ot wa fins el ugha aed a aaa 515 
PENTEL eTICOY OLA © Osis AE ia sail a asta al, Sells diese fe aiaalepicieme Mae ear 515 
PaNeweArcas in Pembrokeshire .........2s.6..c0000seeeenne Peesbas soc 516 
c. Probable Origin and Petrological Characters .................066- 517 
VeHipmene mize DICIAT FLOCKS: 21.220. aseveacsaneitewes og. sveswadsans as Seeaceuevemce 518 
Pmmbigiaencevas tO tAe 05548 ith ceis Teetawe dedesa San nidioas Soeeeermeeee 518 
PeOrem and Petrolopical Characters! ....0-s.c:catesscesse-ssesboeee 519 
Pele OSS OF GY OUP: 02 sada selects a venishin se oroeeenian ot Sea siapbiesiersns sateen 519 
VIII. Detailed Descriptions of Areas near St. David’s..............-.ceeeeees 520 
1. Caerbwdy Valley and Area south-east of St. David’s...............085 520 
Pac ambprian Conglomerates!) (0 2iis.cseen im cece och ec cea eeaeauee 520 
6. Cambrian Succession and Mineral Composition of the beds ... 521 
mer oibsicim det heir sHALeGES c. oss wmcasaeonanandaemacecese ce acaeaeenah odes 522 
Gapeee-Cambprian Rocks im this, Area... csacescnes censs eens esse oeee 523 
2. Nun’s Chapel District and Area south of St. David’s ............... 524. 
papmerca-elais, and Atlan Valley © cit oececs. cz ostdacnse sete cee asemeeee ool 
PON MCS OTIC. si c.ics./va<5 San nsiaesttoelem does lseoae ance a teiable eR seuseacete aes 536 
Meeorun-lisky and Ramsey Sound. ...........ccwcsesseredeescceeesrsceemee 940 
6. Whitesand Bay, Rhosson, Clegyr Hoig, &¢. .......cecc.s-socoseessnees 542 
eS vices Allan, Valley, Sic. ooo. sccccchoesen sees otacsesaerccactenee ones 544. 
aM VAUUSLATIC! 25: weiss: . ose waste iddaekonnee nee racdcunsemeuceene eames 545 
DIMMPMRO em STOMIS Feats 0's sesh. a danage sla eta cs wiely cles ves eeeien me eens see eeeeae 546 
PP PIMC sf bla Lode sober sew vieelden's oeula stele cuive tae pele eee Ree aE 548 
I. lyrropuctrion. 
THE papers on the Pre-Cambrian Rocks of St. David’s which I com- 
municated to the Geological Society in the years 1876, 1878, and 
1879, gave the facts concerning those rocks so far as they were then 
known. Since then I have revisited that district on several occa- 
sions, and have been able to obtain very much additional informa- 
tion in regard tothem. Most of this has proved highly confirmatory 
of my previous conclusions, and it has shown that all the main points 
insisted upon in those papers are correct. Some of the evidence 
has tended, however, to cause me to adopt minor modifications of 
the views expressed ; but this is only what I was quite prepared 
