126 Bulletin 29 290 



species and collected ourselves approximately eleven hundred 

 shells of all sizes ranging from 1.5 to 5.5 mm. The smaller agree 

 with the metatypes, which are 2-3 mm. long. 



I have vainly tried to separate out the larger which inter- 

 grade and show no constant differences. They often have var- 

 ices The Floridian analogue is B. boiplex Dall, and the related 

 Gatun shell is B. Scotti B. and Pils. The Dominican species has 

 not been found elsewhere. 



Locality. — (Exp'd '16) Bluff 3, Cercado de Mao. (Ex- 

 tremely abundant). 



Bittium canaliculatum Gabb 



Plate 2i, Figure 18 



Bittium canaliculatum. Gabb, Trans. Amer. Phil. Soc., vol. 15, p.' 239, 

 1873= 



Our metatypes from Gabb show considerable variation, but 

 one is obviously identical with our specimens. This species has 

 not heretofore been figured. We found it a comparatively rare 

 shell. 



Locality. — (Exp'd '16) Bluff 3, Cercado de Mao. 



Genus Potamides Brongniart 

 Potamides dentilabrum Gabb 



Cerithium dentilabrum Gabb, Trans. Amer. Phil. Soc, vol. 15. p. 237, 

 1873- 



We have an imperfect metatype from Gabb of this interest- 

 ing, unfigured shell. The biplicate columella and dentate outer 

 lip seem to place it in the sub-genus Terebralia Swainson, now 

 found in Borneo. 



Potamides Ormei, n. sp. 

 Plate 22, Figure 8 



Shell rather large, solid; whorls flattened, coarsely cancel- 

 lated by the intersection of many close-set, longitudinal ribs, 



