MOLLUSCA. 55 



MOLLUSOA. 



The localities with which we are at present dealing are, on the whole, very 

 prolific in the remains of shells, but these remains are often both obscure and 

 fragmentary. No doubt this is due for the most part to the effects of fossilization, 

 and to the intractable nature of the rock, which renders it almost impossible to 

 develop any part of a specimen that is covered with matrix. But it is also due 

 to some extent to the animals having died before the deposition of the shells in 

 their present places. The latter is especially the case in the upper part of the 

 Lummaton Quarry, where multitudes of broken shells are crowded together in a 

 way that shows that it must have been a shell-heap in the Palaeozoic Sea. 



While most of the Trilobites that we have described came from Lummaton 

 and few from Wolborough, it will be seen that the contrary is the case with the 

 Cephalopods and Gasteropods. The Pelecopoda are about equally divided between 

 the localities ; but a reference to Dr. Davidson's Monograph shows that in the 

 Brachiopods Lummaton again takes the decided lead in the number of species. 

 The shells from Chircombo Bridge are very few, but Chudleigh has yielded a fine 

 series of Gasteropods to Mr. Vicary's persevering search, and it is interesting to 

 find that the shells from this locality are in a very much better state of preservation 

 than is usually the case. Mr. Vicary has exemplified this in a striking manner 

 by placing a few specimens of recent shells in his drawers alongside of his fossils, 

 and in one or two instances it is almost impossible at first sight to distinguish 

 them by their general appearance. 



Though not surpassing the average of other classes in the number of species, 

 the Brachiopods far exceed them in the number of specimens, almost all the 

 abundant shells belonging to that class. 



Class.— CEPHALOPODA. 



Phillips described nineteen species of Cephalopoda as occurring at Newton ; 

 but, of these, two appear to be repetitions, and another. Nautilus germanus, proves 

 to be a Gasteropod. This number is now raised to fifty-five species from the two 

 localities of Wolborough and Lummaton. These are divided between the genera 

 Goniatites (15), Temnocheilus (1), Trochoceras ? (6), Gyroceras (7), Cyrtoceras (6), 



