Class LAMELLIBRANCHIATA. 



I have preferred the use of the name Lamellibranchiata for this group 

 of molkisks, because it appears to me more appHcable than any other one 

 of the very many names proposed. It may be objected tliat it is a long and 

 difficult name, but that is its only objection ; while most of the others either 

 imply zoological falsehoods when applied to some portions of the group, or 

 are equally applicable to other groups than this one, and I do not see but 

 that the name I have adopted is as generally used, or even more generally 

 used, at the present time than any other. There seems, however, to be 

 a growing tendency with many Conchologists to use the name PeJeeypoda, 

 proposed b}' Goldfuss in 1820 (meaning hatchet-footed), which, to my 

 mind, is particularly objectionable, as there are large groups of these 

 animals where the foot is entii-ely obsolete, or so nearly obsolete as to 

 be without definite form. I do not, however, think this the place to enter 

 into an elaborate discussion of this matter, but will refer those who wish for 

 knowledge on these subjects, to the various manuals of moUusca which have 

 been published, and particularly to the very learned and able remarks of Dr. 

 Stoliczka in the opening chapter of his work on the ^^Pelecypoda" of the Cre- 

 taceous rocks of Southern India, Palseont. Indica, Vol. 3, p. 7, et seq., al- 

 though I entirely disagree with his choice of name for the group. 



In regard to the matter of arrangement or classification which I have 

 adopted in the work, I have a word to say. It will at once be noticed by 

 almost every modern student of concholog)^ that my arrangement is old, 

 and that it is nearly the reverse of that used by writers on recent con- 

 chology. My reason for this is that it accords so much more nearly with 

 the course of nature, as evinced by the successive appearances of the 

 different groups in the geological record. By this I mean an arrangement 

 from the lower toward the higher in zoological structure. It may be said 



