382 PROCEEDINGS OF THE ACADEMY OF [PaRT II 



occasion to refer to it since. The occurrence of a specimen in the 

 ".61ake"dredgings, which, if not identical with Gabb's type is evi- 

 dently closely related to it, enables nie to state that its proper position 

 is probably in this family [Trichotropidae] Unhappily, the operculum 

 and soft parts are wanting so that I cannot confirm my opinion by 

 reference to the details of its organization. I am inclined to be- 

 lievethat another form, also represented in the "Blake" dredgings, is a 

 representative of a shell described as a Melanopsis by Guppy, which 

 Gabb himself suspects to be closely related to his Dolophanes 

 ■melanioides. All these specimens are fresh, but the slight traces of 

 epidermis, which they retain, are not of the character of the northern 

 species of Trichotropis. Their variations are such that I am led to 

 believe all three may be merely mutations of one specific form. If 

 this be confirmed, the specific name of capvla, given by Guppy, is 

 the oldest. Whether the differences are sufficient to constitute for 

 Dolophanes a rank higher than that of a mere section of the genus 

 Trichotropis, a more thorough knowledge of its characters is needed 

 to determine. This pretty and peculiar form is named in honor of 

 the late Wm. Gabb, to whom the generic name is due. I cannot be 

 certain without a comparison of specimens whether the present 

 shell is the same as that described by Prof. Gabb, or not. But the 

 figure is so much like our shell that I can hardly doubt they are very 

 closely related if not the same." 



After a careful comparison with the groups mentioned above and 

 others, we are convinced that Crepitacella belongs to the Rissoidae. 

 According to the principles of the arrangement in Tryon's Manual 

 of Conchology, Vol. IX, it would be a subgenus of the genus Ris- 

 soina, close to the Section Morchiella Nevill; but the absence of a 

 labral varix may make it expedient to treat the group as generic, 

 though close to Rissoi)ia. 



As to the specific synonymy, we are satisfied that the form of the 

 Bowden bed, Jamaica, and that of Santo Domingo named D. melan- 

 ioides by Gabb, are specifically identical, though there are some 

 differences, the Jamaican form being of a somewhat stouter, more 

 robust shape. The type of D. melanoides measures, alt. 13.7, diam. 

 7 mm., length of aperture 6.8 mm. (Plate XXXIV, fig. 12). From 

 the descriptions and figures it does not appear likely that any of 

 the other forms included in the list given above is specifically dis- 

 tinct. 



The type of D. melanoides is no. 4077 A. N. S. P. 



Rissoina (Zebina) laevigata (C. B. Ad.) Plate XXXIV, figs. 3, 4. 



Eulima craasilabris Gabb, Tr. Am. Philos. Soc, xv, 1873, p. 227. Not 



Rissoa crassilahrum Garrett, 1857, also a Zebina. 

 Rissoa laevigata C. B. Ad., Contrib. to Conch, 1850, p. 114. 



