1868.] noLL — SOUTH devon and east coenavall. 449 



it occurs in the Pctherwin beds ; and, lastly, there are 6 Brachio- 

 pods named hj Mr. Ethcridge* as being- characteristic of the North- 

 Devon Upper Devonian rocks, and not occurring below them, viz. 

 Athyris ohlonga, JJiscina nitida, Lingula squnmiforinis, Prodiictus 

 scahricidus, Terebratula sacculus and lihynclionella acuminata f , none 

 of which are known in the Petherwin beds. 



These results, so far as they go, are, I believe, in accordance 

 with those of Mr. Salter J, who, reasoning from the mixed cha- 

 racter of the Petherwin fauna, consisting partly of Upper- and partly 

 of Middle-Devonian forms, assigned to these beds a middle position 

 between the fossiliferous zones of the two upper divisions of the 

 Devonian system, or, at any rate, a place below the Marwood beds ; 

 and he gave, among other reasons for doing so, the presence of Gly- 

 menia and Cardiola rostrata. This method of reasoning, however, 

 can hold good only so long as there is no evidence of stratigraphi- 

 cal superposition. That Cardiola rostrata lived in Upper-Devonian 

 times on the Continent is no evidence that it did not exist in Middle- 

 Devonian times in Britain ; and perhaps a rigid comparison of the 

 Devonian fauna of North America and elsewhere with that of 

 Devonshire and continental Europe might throw some additional 

 light on our knowledge respecting the migration of species, and 

 their distribution in time and space. 



The beds brought up by the narrow anticlinal axis at Yealm 

 Bridge may perhaps be rather higher in the series than the Pether- 

 win rocks ; but of this there is no evidence. The fossils are Phacops 

 latifrons, Entomos? (Cypridina) serrato-striata^, and Petraia Cel- 

 tica, which are likewise Petherwin fossils, with Sanguinolaria ellip^^ 

 tica, Phill., and Bellerophon hiidcus, Sow. ; but these latter, as we afe 

 told by Mr. Pattison ||, were found in the loose upper layers ; and 

 it is not quite clear whether or not they may belong to the Upper 

 or Carbonaceous system. 



In endeavouring to determine the position of the fossiliferous 

 rocks of Liskeard and the Looe- river district by means of their 

 organic remains, we are embarrassed by the want of evidence ; for 

 although vast numbers of casts of fossils have been observed, they 

 are mostly in such a wretched condition that only a few of them 

 have been identified specifically. Besides the forms enumerated 

 in the following Table (Table III.), species of Orthoceras, of Brachio- 

 poda, and of Ccelenterata have been noticed in the neighbourhood 

 of Liskeard ; and it was from within this area that Mr. Pengelly 

 obtained the Phacops punctatus figured in Mr. Salter's monograph^. 

 In the Looe-river district, including Poluran, Eowey, &c., and the 

 shores of Whitesand Bay, other species, not included in the Table, 

 have been found, of the genera Aviculopecten, Avicula, Ctenodonta^ 



* L. c. p. 668. 



t L. c. p. 668. A seventh is given in the text, viz. Spirifera Urii ; but this 

 species occurs at Barton, and is recorded as a Middle -Devonian species in 

 Tables 2 & 9 of the Memoir- } Quart. Journ. Geol. Soc. vol. xix. p. 483, 



§ On the authority of Mr. S. E. Pattison. 



II Trans. Eoyal Geol. Soc. of Cornwall, 35th Ann. Eep, p. 64. 



^ Pakeont Soc. Mon. Trilobites, pt. 1. pi. i. figs. 17-19. 



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