Gasteropodous Mollusca into larger Groups and Families. 125 



rostrum, while tlie gi-eater part of the species are properly re- 

 presented without it, and as having a proboscis, and the same 

 may be remarked of some of the more modern figures of these 

 animals. 



I fully expect that many naturalists, especially those who have 

 chiefly confined their studies to the external form of shell or to 

 the fossil species, will consider that the system here proposed is 

 very artificial, as it separates many genera and families from one 

 another which they have regarded as being very nearly allied, or as 

 belonging to the same family or even genus. But it must be re- 

 collected that this was the case when first the study of the animal 

 was undertaken, yet no one now objects to the terrestrial Helices 

 and Bulimi being separated from the sea shells which were formerly 

 arranged with them, or the Bullce from the other marine families, 

 and we must expect that as the structure of the animal becomes 

 more known, the more the genera founded only on the shells will 

 become separated and dispersed. 



In drawing up the characters of the suborders and families, 

 I have attempted to select those which appeared most perma- 

 nent, or least subject to variation. In all animals, as a general 

 rule, those organs by which they obtain their food belong to the 

 first class ; hence the characters of the suborder and its divi- 

 sions have been taken from the form of the mouth and the 

 disposition and form of the teeth on the lingual membrane, as I 

 have no doubt these parts have a most important bearing on the 

 oeconomy of the animal ; while the characters of the families 

 have been taken from the modifications of the mantle and differ- 

 ences in the structure and form of the operculum and shell; 

 for though I consider that the characters of the order, suborder, 

 and families should be chiefly taken from modifications of the 

 animal, I always consider that the shell and operculum are 

 quite as important as regards the genus, as the animal which 

 forms it. 



Suborder I. Proboscidifera. Head small, with an elon- 

 gated, retractile, longly exsertile proboscis, when retracted hidden 

 within the body ; tentacles close together at the base or united 

 by a veil over the base of the proboscis j eyes sessile, on the outer 

 base of the tentacles ; operculum annular (except in Natica). 

 Carnivorous, eating living mollusca and other animals. 



The trunk or proboscis is of a very complicated structure and 

 furnished with a number of muscles, well described by Cuvier in 

 his anatomy of Buccinum, which enable it to be withdrawn into 

 itself like the tentacles of a snail. These animals are said to 

 form the round holes so commonly found on other shells, and 

 the lingual membrane is placed near the apex of the exserted 

 trunk. 



