RETUSA. 221 



lias a shallow rounded notch, the outer boundary of whose patli is 

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

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

 arched forward in the middle ; ])illar 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 fascicle 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*() ; max. 

 lat. 2-5; lat. of apex 1-5 mill. (DalL). 



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

 dos, in about 80 fms., sand. 



Utriculus pervms 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.). 



R. OMPHALis Morch. Unfif/ured. 



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

 obsolete growth strife, regular and elegantly expressed toward the 

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

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

 posteriorly, dilated anteriorly ; columella straight, thick ; external 

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



St. Thomas (Riise). 



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



Not dissimilar from CyUchnella bidentata, but larger, thinner, 

 with umbilicate spire and straight columella, etc. (il/.) 



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. 



Ca^ye Halter as ; West Indies, 14-31 fms. 



Bulla sulcata Orb., Moll. Cuba i, p. 129, pi. 4 bis, f. 9-12.— t7i!rt- 

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

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



