RETUSA. 221 



has a shallow rounded notch, the outer boundary of whose path is 

 marked by the summit of a raised line ; anterior part of aperture 

 wider, not very oblique, rounded in front ; outer lip straight, thin, 

 arched forward in the middle ; pillar thin, simple, with no trace of 

 a plait ; body without perceptible callus ; behind the pillar a small 

 very deep umbilical perforation ; apex nearly flat, bounded by the 

 above mentioned raised line, within which the fasciole of the notch 

 is rounded over but does not reach the level of the line referred to ; 

 nucleus somewhat depressed, but not deeply ; about three and a 

 half whorls are visible on the apex. Max. Ion. of shell 4*0 ; max. 

 lat. 2-5; lat. of apex T5 mill. (Dall). 



West Indies (U. S. Fish Commission), probably from near Barba- 

 dos, in about 80 fms., sand. 



Utriculus pervius DALL, Blake Gastr. p. 48. 



This species is remarkable for its deep though minute umbilicus 

 and its dish-like apex. Its general form is not unlike U. perplica- 

 tus, but the sides are straighter and the other characters quite dif- 

 ferent. The locality is unfortunately doubtful though it was some- 

 where in the Antilles (Dall.). 



K. OMPHALIS Morch. Un figured. 



Shell subcylindrical, short, slightly contracted in the middle, with 

 obsolete growth strife, regular and elegantly expressed toward the 

 spire ; spiral striae very obsolete, irregular. Spire openly umbili- 

 cated, surrounded by a white pellucid line. Aperture very narrow 

 posteriorly, dilated anteriorly ; columella straight, thick ; external 

 margin acute. Alt. nearly 4, diam. 2 mill. (M). 



St. Thomas (Riise). 



Retusa omphalis MORCH, Malak. Bl. xxii, p. 172, 1874. 



Not dissimilar from CylieJinella bidentata, but larger, thinner, 

 with umbilicate spire and straight columella, etc. 



R. SULCATA Orbigny. PI. 23, figs. 73, 74. 



Shell cylindrical, white, dilated below, thin, pellucid, longitudi- 

 nally sulcate, truncated at summit and concave, the spire umbili- 

 cated. Aperture linear, suddenly dilated below. 



Alt. 2, diam. 1 mill. 



Cape Hatter as ; West Indies, 14-31 fms. 



Sulla sulcata ORB., Moll. Cuba i, p. 129, pi. 4 bis, f. 9-12. Utri- 

 culus (Retusa) sulcata DALL, Blake Gastr. p. 45 ; Cat. Mar. Moll. 

 .S. E. U. S, p. 86. 



