395 
Mr. Dillwyn on fossil shells. 
Every turbinated univalve of the older beds from transition 
lime to the lias, which I have been able to procure, or of 
which I can find any record, belongs to these herbivorous 
genera, and the family has been handed down through all 
the successive strata, and still inhabits our land and waters. 
On the other hand, all the carnivorous genera abound in the 
strata above the chalk, but are comparatively extremely rare 
in the secondary strata, and not a single shell has been de- 
tected in any older bed than the lower oolite. As a proof of 
this rarity it may be remarked, in the list of British fossils 
which Mr. Parkinson has given in his Introduction to the 
Study of Organic Remains, that not one single species of 
either of the carnivorous genera has been referred to any 
stratum below the London clay, and only the few following 
species appear in any of the numerous lists of the secondary 
strata which are given in Conybeare and Phillips' Outlines 
of Geology, viz. a Murex* and Pleuroioma rostrata in the 
green sand, Cerithium melanoides in chalk marie, and a few 
species of Rostellaria in various strata from chalk marie to 
the lower oolite. For the Pleurotoma and the Cerithium, a 
reference to the Mineral Conchology is given ; and Mr. 
Sowerby there only says that he has seen an imperfect cast, 
very like the former, from the canal at Devizes ; and of the 
latter, that it was found in the London clay, and in the clay 
above the chalk at Newhaven. It is also worthy of remark, 
that all the above-mentioned Rostellarise which have been 
found in secondary strata are nearly allied to the Linnsean 
* Mr. George Sowerby has sent me this shell with the name of Murex calcar, 
and if I am not much mistaken, I have seen another species of Murex from tne 
green sand in the extensive collection of Mr. J. S. Miller. 
