173 Panama Shells. LiTa'OBiNiDiB, 



245, Rissoa fortis. Nov. sp. 



Shell long, ovate conic : white : with, on each whorl, about 

 twenty -two to twenty -four stout prominent approximate ribs, 

 which converge at the anterior extremity, where they become 

 very small : ' apex acute ; spire with the outlines curvilinear : 

 whorls ten, slightly shouldered, moderately convex, with a well 

 impressed suture ; last whorl ventricose ; aperture oblique, 

 ovate, retreating above, deeply effuse ; labrum much advanced 

 in the lower half, very thick : labium thick : umbilicus want' 



ing. 



Mean divergence about 33°; length .29 inch; breadth ,12 

 inch ; length of spire .185 inch. 



This species resembles B. ambigwi Gould, and is very different 

 from Rissoina Inca Orb. 



Station. — Under stones near low water mark. 



Habitat.— Tahoga. ; 0. B. A. ! 

 31 specimens were collected. 



246. Rissoa (I) inconspiciia. Nov. sp. 



Shell ovate conic : white : with several spiral ridges, of which 

 two or three are seen on the spire : with about twelve or four- 

 teen transverse narrow ridges, which are obsolete anteriorly: 

 apex subacute : spire with curvilinear outlines : -whorls four, 

 very convex, with a deep suture : last whorl rather ventricose, 

 short : aperture orbicular, scarcely effuse ; lip well thickened ; 

 with a very minute umbilicus. Perhaps this species should 

 have been referred to Cingula. 



Mean divergence about 55° ; length .045 inch : breadth .03 

 inch ; length of spire .032 inch. 



Station. — Unknown. 



Habitat- — Panama ; 0. B. A. I 

 1 specimen was obtained. 



