448 PROCEEDINGS OF THE GEOLOGICAL SOCIETT. [April 22, 



Now, of these 45 species, 27 are said to occur in the upper group of 

 North Devon ; but, on the other hand, there are in the Upper North- 

 Devon group 78 species which do not occur in the Petherwin beds. 

 But there are 37 species in common between Petherwin and the 

 Torbay or South-Devon limestones ; and if to these we add 3 addi- 

 tional species from the Middle North-Devon or Dfracombe group, 

 this will make 40 species, and two others from the beds which 

 underlie the Torbay hmestones will give a total of 42 species out 

 of 45 as common to the Middle Devonian and the Petherwin rocks, 

 against 27 in common between Petherwin and the Upper North- 

 Devon group. This leaves but 3 species that are not found in the 

 Middle Devonian rocks of Devonshire, exclusive of the 31 that are 

 peculiar, viz. Avicula transversa, Murcliisonia angulata, and Ortho- 

 ceras striatum*, which are Upper-Devonian and Carboniferous species. 

 The affinity, therefore, of the Petherwin fauna with that of the 

 Upper North-Devon group is not so strong as it is with that of the 

 Middle group of South Devon. 



If we compare the Petherwin fauna with those of the Upper and 

 Middle groups of the European continent, the results are nearly the 

 same. Deducting from the 76 Pethermn species the 21 not found 

 elsewhere, we have 55 species remaining, of which 18 occur in Con- 

 tinental Upper, and 24 in Continental Middle Devonian rocks. And 

 if we compare the same 55 species with the fauna of the Upper and 

 Middle groups of aU areas collectively, we have 33 for the Upper 

 and 48 for the Middle group in common. Of these, 3 species are 

 met with common to Petherwin and the Upper Devonian group that 

 do not occur in the Middle group, against 18 species common to 

 the latter and Petherwin that do not occur in the Upper group, but 

 of which two species, viz. Poterioceras fusiforme and Loxonema 

 tumida, occur also in Carboniferous rocks, and, possibly, do not 

 reaUy belong to the Petherwin lower fauna t. 



To pass to particular species, it may be observed that some im- 

 portance has been attributed to the occurrence of Cypridina (En- 

 tomos) serrato-striata, Sand., in the Petherwin rocks, as it was for- 

 merly supposed to be a characteristic fossil of the Upper division 

 of the Devonian system ; but it is now known to occur likewise in 

 the Middle division. The Clyrtienice, again, have been appealed to 

 as evidence of the Upper- Devonian character of the Petherwin 

 beds ; but of the 1 1 species that have been met with in that locality, 

 8, according to Mr. Etheridge's lists, appear to be unknown else- 

 where, and therefore tell us nothing. Of the 3 remaining species 

 2 are true Middle-Devonian forms, and the other is a Middle- 

 Devonian species in South Devon (and on the Continent?), and an 

 Upper-Devonian form in Erance. On the other hand, the genus 

 Cyrtoceras is not known in true Upper Devonian rocks, nevertheless 



* This last is not contained in Prof. PhiHips's lists. 



t In a paper " On the G-eological and Chronological Distribution of the De- 

 vonian Fossils of Devon and Cornwall," published in the ' Geologist ' for 1862, 

 Mr. Pengelly arrived at the conclusion that the Petherwin beds were " somewhat 

 more ancient than those of Barnstaple." 



