EAST AMERICAN SCAPHOPOD MOLLUSKS. 



93 



On account of the fragility of these apical features in small delicate 

 shells it is often difficult to assign any species positively to this group. 



KEY TO THE SPECIES OF THE SUBGENUS PULSELLUM. 



Shell rather strongly curved, length 5 mm bushi, page 94. 



Shell slightly curved, length 3.15 mm occidentale, page 93. 



SIPHONODENTALIUM (PULSELLUM) OCCIDENTALE, new species. 



Plate 16, fig. 4. 



1880. Siphoentulis lofotensis, Verrill, Amer. Journ. Sci., vol. 20, p. 392 (not of 



Sars, 1864). 

 1880. Siphoentalis h/otensis, Verrill, Proc. U. S. Nat. Mus., vol. 3, p. 395 (not 



of Sars). 

 1882. Siphoentalis lofotensis, VERRihL, Trans. Conn. Acad, of Arts and Sci., vol. 5, 



pt. 2, p. 558 (not of Sars). 

 1884. Siphoentalis lofotensis, Bush, Report of Com. of Fish and Fisheries for 1883, 



vol. 17, p. 717 (not of Sars). 

 1897. Siphonodentalium (Pulsdlum) lofotense, Pilsbry and Sharp, Tryon's Man. 



Conch., vol. 17, p. 138, in part and omitting all figures. 

 1915. Siphonodentalium (Pulsellum) lofotense, Johnson, Occ. Papers Boston Soc. 



Nat. Hist., vol. 7, No. 13, p. 84 (not of Sars). 



The shell is very small, thin, fragile, slightly curved, moderately 

 tapering, with a relatively large apex, round section, and oblique 

 aperture. In color it is a translucent white, with milky white bands or 

 growth rings, and some opaque patches. It has no sculpture nor 

 apical notch nor lobes. 



The type, Cat. No. 38702, U.S.N.M., measures— length, 3.15 mm.; 

 diameter, 0.5 mm. It was taken at the U. S. Bureau of Fisheries 

 Station 871 off Marthas Vineyard in 86 fathoms. 



Critical comparison of many of our western Atlantic species with 

 actual types or authors' specimens of European species (hitherto 

 considered conspecific with them), has led me to separate them at 

 least subspecifically. I feel, therefore, that it requires substantial 

 evidence to establish the specific, or especially a subspecific, identity 

 of mollusks from the two sides of the Atlantic. These tiny, fragile 

 little shells, almost featureless and usually broken and fragmentary, 

 can not furnish this evidence. Were a larger proportion of the spe- 

 cies of the two faunas really identical I would then consider the burden 

 of proof to be upon the one who would separate rather than upon him 

 who seeks to unite them. The museum records given below indicate 

 this to be a species of the lower continental slope and of northern 

 ranofe : 



