640 SYSTEMATIC PALEONTOLOGY 



when it takes the clavicular form, as, in different species of the same group, 

 and even in individuals of the ^ame species, its size and prominence vary 

 very greatly. Adriatic specimens of the typical species, C. cuspidata, 

 show a strong buttress; British specimens of the same species often show 

 it faintly or not at all, while otherwise well developed. The names 

 Naera, Rhinomya, Aulacophora, Spathophora, and Trophidophora, among 

 those which have been applied to members of this group, by Gray, Adams, 

 and Jeffreys, are all preoccupied in zoological nomenclature, some of them 

 several times over. 



" The characters of radiating and concentric sculpture in this group 

 have no more than a specific value ; there are few species where they tire 

 not more or less combined in the external ornamentation. The surface 

 may be polished, smooth, wrinkled, sulcate, or granulous. The anterior 

 muscular scar is double or single, the posterior scar double, in all the 

 specimens I have seen where the scars could be made out." Dall, 1886. ' 



The genus was initiated in the Mesozoic and persists in the recent seas 

 as one of the characteristic deep water forms. One species, C. lucifuga 

 Fischer, has been reported from over 2500 fathoms. 



A. Latitude of adult shell not exceeding 8 mm.; anterior portion of shell 



not evenly inflated, tending to flatten toward the anterior lateral and 

 ventral margins Cuspidaria ampulla 



B. Latitude of adult shell exceeding 8 mm.; anterior portion of shell 



evenly inflated, not flattened toward the anterior lateral and ventral 

 margins Cuspidaria cucurbita 



CUSPIDARIA AMPULLA n. sp. 

 Plate XXXVII, Figs. 6, ? 



Description. Shell small, even for the genus, thin, approximately 

 equivalve, strongly inequilateral, highly inflated in the umbonal region 

 and the medial portion of the disk, flattening a little toward the anterior 

 and ventral margins of the shell and abruptly compressed posteriorly; 

 umbones inflated even to their apices, proximate, incurved, feebly opistho- 

 gyrate, rising well above the dorsal margin, a little in front of the median 

 horizontal; anterior dorsal margin steeply descending; posterior dorsal 



1 Bull. Mus. Comp. Zool., Harvard Coll., 1886, p. 292. 



