Lingula Flags. 63 



both areas there is a lithological passage and con- 

 formity between the Cambrian and Menevian strata, 

 fig. 62, p. 322. 



Four species of sponges are at present known in 

 the Menevian beds of St. David's, named by Mr. Hicks. 

 They are all of his genus Protospongia, and one of 

 them, P. fenestrata, is found in the underlying Cam- 

 brian strata, also one Cystidean, Protocystites Mene- 

 vensis, a few Annelid tracks, and more than thirty 

 species of Trilobites of the genera Agnostus, Arionellus, 

 Anopolenus, Conocoryphe, Erinnys, Holocephalina, 

 Paradoxides, and Carrausia. Of these, seven species 

 belong to the genus Agnostus, one of which, A. Cam- 

 brensis, is also found in the Cambrian rocks, as its 

 name implies. There are seven species of Conocoryphe, 

 three of which are also Cambrian species, viz. C. ap- 

 planata, C. Bufo, and C. humerosa. Paradoxides 

 aurora is also common to both formations, and a few 

 Brachiopoda, such as Discina pileolus, Lingulella 

 ferruginea and Obolella sagittalis. Of Pteropods the 

 genus Theca is common, but, as far as I know, no 

 Lammellibranch molluscs or Gasteropoda are found 

 in these strata. 



The Lingula flags rest conformably on, and in fact 

 pass by lithological gradations into the Menevian beds 

 (fig. 62, p. 322). They are best developed in Merioneth- 

 shire, Carnarvonshire, and at St. David's, and consist of 

 black and gray slaty rocks with beds of grit. 



In these a marked and distinctive suite of fossils 

 occurs, the chief of which are Lingulella Davisii, and 

 many genera of Crustacea Conocoryphe bucephala 

 and two others, Agnostus (4), Paradoxides (2), Holo- 

 cephalina (1), Anapolenus (2), Erinnys, and Cono- 

 cephalus all Trilobites ; also a phyllopod crustacean, 



