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In the Zeitschrift fur Malac. R. scnlarella is referred to the genus 

 Rissoina, on account of the presence of a solid calcareous operculum. 

 Some fresh specimens obtained by me near Kingston in 1844, were 

 found to have a horny operculum. 



RissoA LAEVIGATA. Shell long ovate conic, rather slender : white, 

 translucent : smooth : apex acute : spire with the outlines slightly 

 convex : whorls nearly seven, scarcely convex, with a moderately 

 impressed suture : aperture moderately effuse : labrum well advanced 

 and excurved, rather thick. 



Mean divergence about 28*^ ; length of spire .08 inch ; total length 

 .12 inch ; breadth .045 inch. 



RissoA DUBiosA. Shell long ovate conic : white, translucent : 

 with, on each whorl, nineteen or twenty obtuse ribs, which are pro- 

 duced on the last whorl to the anterior extremity : apex subacute : 

 spire with the outlines moderately curvilinear : whorls seven, rather 

 convex, with a well impressed suture : aperture moderately effuse : 

 labrum well advanced : excurved, moderately thickened. 



Mean divergence about 28°; length of spire .115 inch; total 

 length .185 inch ; breadth .065 inch. 



RissoA PULCHRA. Shell subovate, turrited : white, with a pale 

 yellowish brown spiral band on the upper part of the whorls, and a 

 similar band anteriorly : with spiral ridges increasing from two on 

 the upper whorls to four or five on the penult whorl, (of which the 

 upper one is smaller,) and on the last whorl seven, which are crossed, 

 with well developed nodulous intersections, by twenty to twenty-two 

 small transverse ridges ; anteriorly with three nodiferous approximate 

 spiral ridges, which are separated from the other seven by a broad 

 groove : apex acute: spire with the outlines moderately curvilinear : 

 whorls ten, quite convex, with a well impressed suture : aperture 

 very effuse : labrum well advanced and excurved, very much thick- 

 ened. 



Mean divergence about 22°; length of spire .155 inch; total 

 length .225 inch ; breadth .08 inch. 



RissoA MULTicosTATA. Shell ovate conic, turrited : white: with 

 on each whorl, about twenty-eight very regular ribs, which are pro- 

 duced on the last whorl to the anterior extremity, and numerous dis- 

 tinct spiral striae on the anterior half of the last whorl, which impress 

 the summits of the ribs ; on the rest of the shell between the ribs are 



