8 CRETACEOUS PELECYPODA 



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

 (1830) replaced by elatobrancsia. 



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

 evidently with tlie object of ol)taining uniformity with the nomenclature of the 

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

 name Pelecypoda has regard to the very usual hatchet-shape of the i'oot, its 

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

 Burmeister suggested in 184!3 the name cormopoda, 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 r(;garding 

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

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

 it seems not desirable that the number should bo 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 Mollusca, provided, 

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

 type, (an opinion upon which, I believe, 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 thei'e are 

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

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

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

 nation. The names lamellibranchiata, or elatobrancsia, have, on the contrary, 

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

 them, as to the two former names : First, there is nothing chai'acteristic or 

 peculiar in the lamellar shape of the gills which does not occur in otlici', chiefly 

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

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

 — bntnchia not eligible. The third name is Bronn's elatocephala. I have due 

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

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

 been referred to the larger division, " mollusca acephala," and then immediately 

 called " elatocepuala,'" 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 



* 1 would i-couinnienj to tliose wlii) object to the t^rm Pt'lecypoda. on tin- plea tliat the foot of these animals is not 

 always hutchet-shajx'd, the study of the various forms of hatchets and battle-axes of the uiiddlt aije. 



