CAMBRIAN. 



WALES AND WEST OF ENGLAND. 



L WER CAMBRIAN. 



The Lower Cambrian rocks are often subdivided geographically, 

 or according to the several tracts over which they are exposed. 

 Two well-marked series are, however, now established : — 



2. Menevian Series. 



I. Harlech and Longmynd Series. 



Together they comprise two palseontological divisions, being marked 

 by the presence of Paradoxidcs and Annelides. They are arranged 

 as follows •} — 



■r, J -i- { 2. Menevian Series. 

 I'araaoxiaian \ tt i u j t j c ■ 



'. I. Harlech and Longmynd Series. 



' 2. Solva Group. 



Annelidi'ati i- Caeifai Group. 



The thickness of the Lower Cambrian rocks varies in different 

 areas, the estimates being from about 4000 to upwards of 8000 feet.^ 



HARLECH AND LONGMYND SERIES. 



This series, named by Sedgwick, includes the Harlech, Long- 

 mynd, and Llanberis Beds ; and the Caerfai and Solva Beds, which 

 have been more recently distinguished, in South Wales. The sub- 

 divisions have not been correlated with precision. 



The rocks consist of a series of grey, purple, and red flaggy 

 sandstones, conglomerates and shaly beds, having a thickness 

 estimated at from 3500 to 4000 feet in South Wales, and supposed 

 to be over 8000 feet in North Wales. Remains of Sponges, 

 Annelides, Pteropods, Polyzoa, Brachiopods, such as Lingtdella 

 and Oboldla ; also of Entomostraca, and Trilobites of the genera 

 Conocoryphe, Paradoxides, Microdisciis and Plutonia, have been 

 determined in these strata, mainly through the researches of Dr. 

 Hicks. The earliest British Brachiopod (^Lingulella primava or 



1 C. Lapworth, G. Mag. iSSi, p. 321. 



- For remarks on the deposition of the Lower Cambrian beds, see E. Hull, 

 Q. J. xxxviii. 210. 



