8 CEETACEOUS PELECYPODA 



deriyed name elatobranchiata was substituted for it by Menke, and a little later 

 (1830) replaced by elatobrancria. 



In 1820 Goldfuss proposed in his Manual of Zoology the name pelucypoba, 

 evidently with the object of obtaining uniformity with the nomenclature of the 

 other classes of MoUusca, the Cephalopoda, Gastropoda, Brachiopoda, &c. The 

 name Pelecypoda has regard to the very usual hatchet-shape of the foot, its 

 presence and form* being indeed even more constant than in the Gastropoda. 

 Burmeister suggested in 1843 the name gormopoda, evidently having the same 

 object in view as Goldfuss had, but I do not think that the latter name is 

 equally characteristic as the former ; at any rate, it is no improvement upon it. 

 At last Bronn suggested in 1861 the name elatocephala^ though he rather appears 

 to have expressed himself in favor of Menke's elatobranchia. 



Looking at the various names, as noted above, I would at first observe regarding 

 their derivation that an attempt evidently has been made to obtain a denomination 

 which is taken from one of the principal characters of the MoUusca, and, therefore, 

 it seems not desirable that the number should be increased by any other new name, 

 unless its greater usefulness and propriety has been fully established. In making, 

 therefore, a selection from the existing materials, it seems to me not only extremely 

 convenient and desirable, but also natural, that we should observe a uniformity 

 in the denomination of the various classes of the sub-kingdom MoUusca, provided, 

 we admit that those classes are merely modifications of one - the molluscous- 

 type, (an opinion upon which, I beheve, there is hardly a division among 

 naturalists), and that the classes represent those modifications as developed in some 

 or other principal organ. 



The names bivalvia and conchifera have been rejected, because there are 

 other classes of MoUusca and other animals (Brachiopoda, Cirrhipeda, Entomostraca) 

 which possess two valves, wMle there is nothing in the names which would 

 sufficiently characterize the class, and which could be used for a uniform denomi- 

 nation. The names lamellibrancriata, or elatobrancria, have, on the contrary, 

 been thought very appropriate, but it is clear that the same objection appUes to 

 them,^ as to the two former names : Eirst, there is nothing characteristic or 

 peculiar in the lameUar shape of the giUs which does not occur in other, chiefly 

 higher organised, aquatic animals; and then the single fact, that there are MoUusca 

 with lungs as weU as with gills, and some without either of them, makes the term 

 —hrancUa not eligible. The third name is Bronn 's elatoceprala. I have due 

 regard to the importance of cephalisation in classification, but I beUeve the name 

 is here very inappropriately used. The single fact, that the present class had first 

 been referred to the larger division, - mollusca aceprala;' and then immediately 

 caUed '' elatoceprala,'' speaks against it. 



^ None of the above objections are directly applicable to the name Pelecypoda; 

 It not only admits a uniformity in the denomination of the different classes of the 



; \ 7^^J ^^--f *;> ^;^--^^o object to the tern. Pelecypoda, on the plea that the foot of these animals is not 

 always hatchet-shaped, the study of the various forms of hatchets and battle-axes of the middle a.e. 



