115 



rery faintly impressed microscopic spiral striae : apex acute : spire 

 with the outlines moderately curvilinear : whorls seven, quite con- 

 vex, with a well impressed suture : aperture deeply effuse : labrum 

 much excurved and very thick. Conf. Rissoma dcgantissima Orb. 

 Moll, du Cuba, Tab. XII. f. 27-29. 



Mean divergence about 26° ; length of spire .12 inch ; total length 

 .18 inch ; breadth .07 inch. 



RissoA viTREA. Shell ovate conic, turrited : with a scarcely per- 

 ceptible bluish tinge, opaque white at the suture and in the thicken- 

 ing around the aperture ; in the rest transparent as glass, and clearly 

 exhibiting the internal structure : highly polished, with some scarcely 

 perceptible microscopic striae of growth, and a fine impressed spiral 

 line very near and next below the suture : apex very acute : spire 

 with the outlines moderately curvilinear : whorls nearly ten, slightly 

 convex, with a distinct but moderately impressed suture : aperture 

 very effuse and angular anteriorly : labrum very much excurved and 

 advanced, moderately thickened. 



Mean divergence 26° ; length of spire .19 inch ; total length 

 .29 inch; breadth .105 inch. 



RissoA LAEvissiMA. Shell long ovate conic : dingy white, with a 

 very pale reddish brown spiral band on the upper part of the whorls, 

 and two others on the middle and anterior part of the last whorl ; 

 but these bands are often obsolete, and speedily disappear in weather- 

 ing : surface highly polished : apex very acute : spire with the out- 

 lines slightly curvilinear : whorls nine, slightly convex, with a mode- 

 rately iu-pressed suture : aperture rather small, very effuse: labrum 

 well excurved and advanced, very much thickened. Conf. Rissoina 

 Brmvniana Orb. Moll, du Cuba, Tab. XII. f. 33-85. 



Mean divergence about 30° ; length of spire .13 inch ; total length 

 .2 inch ; breadth .09 inch. 



RissoA EULTMOiDEs. Shell elongate conic : white, translucent in 

 a spiral line below the suture : smooth and shining, with a broad very 

 obtuse varix on each whorl, forming a slightly oblique line with the 

 labrum : apex rather obtuse : spire with the axis moderately curved, 

 convex on the left and rectilinear on the right side : whorls seven or 

 eight, scarcely convex, with a lightly impressed suture : aperture 

 scarcely effuse : labrum well excurved, not advanced, moderately 

 thickened. 



