﻿156 DEVONIAN FAUNA. 



Class.— GASTEROPODA, Goldfuss, 1820. 



The Gasteropoda have yielded a much greater variety of species from the 

 localities now under notice than have any other class of fossils. They are, 

 however, very unequally represented in them. By far the largest number come 

 from Wolborough, except in the case of one family, the Capulidse, which is very 

 abundant both individually and specifically at Lummaton. From Chircombe 

 Bridge there are hardly any to record. The small group of species from 

 Chudleigh, on the other hand, includes several shells which are of peculiar interest. 

 These occur chiefly in the Keswell Quarry in a decomposed matrix which has 

 allowed them to be extracted almost uninjured and entire. They are all very rare, 

 with the exception of Murchisonia turbinata, Schlotheim, which has been obtained 

 in very large numbers. This shell is remarkable for the amount of specific 

 variation which it displays. The specimens of it are hardly ever exactly alike, 

 and their great abundance permits us to range under the one species fossils 

 which otherwise we should be obliged to regard as specificially or even generically 

 distinct, and thus enables us to surmise that it is possible that, if we were equally 

 fortunate in some other cases, we might be able to unite several forms which at 

 present we are forced to consider as separate species. 



The number of Univalves described by Phillips was 24, viz. 23 from Newton, 

 1 from Barton, and 1 from Chudleigh — one of which, however, he treated as a 

 Cephalopod. Besides these, eight shells described by him from other places are 

 found to have occurred in the present localities ; but, on the other hand, I have 

 been unable to meet with any examples of one or two of his Newton species, 

 while two or three of the remainder must, as it seems to me, be removed from the 

 list as synonyms. 



The number of species is now raised to about 113, which are divided between the 

 genera Dirhachis (1), Macrochilina (10), Loxonema (7), Michelia (1), Spanionema 

 (1), Littoriua (2), Naticopsis (1), Natica (3), Strophostylus (1), Platyostoma (3), 

 Capulus (15), Orthonychia (2), Holopella (5), Scoliostoma (2), Antitrochus (1), 

 Philoxene (3), Euomphalus (10), Phanerotinus (3), Plagiothyra (2), Rotellina 

 (1), Liotia (1), Flemingia (1), Elasmonema (1), Turbo (3), Pleurotomaria 

 (19), Murchisonia (0), Odontomaria (1), Bellerophon (5), Porcellia (1), Helmin- 

 thochiton (1). 



It is of course very often impossible to fix with any degree of certainty the 

 biological position of these shells, for the mouth is generally obscured or defective ; 

 and the arrangement of the genera is rendered all the more difficult by the fact 

 that under the best of circumstances the shell only gives indirect information of 



