180 Panama Shells. 



249. Rissoa notabilis. Nov. sp. 



Sliell long ovate-conic : white : with, on each whorl, about 

 fourteen transverse very prominent ribs, which have concave 

 summits ; with four spiral keels, of which the upper two are 

 more distant and are seen on the spire on each side of the 

 suture ; the transverse ribs are smaller in the parts between the 

 second .and third keels, and are obsolete below the third : apex 

 subobtuse, smooth and shining : spire with the outlines recti- 

 linear except near the apex : whorls six, abruptly shouldered, 

 planulate, with the suture subcanaliculate : aperture ovate : 

 umbilicus wanting. 



Mean divergence about 24 ; length .06 inch ; breadth .027 

 inch. 



/Station . Unknown . 



Habitat. Panama; C. B. A.! 

 1 specimen was found. 



250. Rissoa scalariibrmis. Nov. sp. 



Shell elongate, ovate conic : dingy white : with, on each 

 whorl, eleven stout prominent acute compressed ribs, which are 

 continuous on the successive whorls ; covered with microscopic 

 spiral stride, which ascend the sides of the ribs but are obsolete 

 on their summits : apex acute : spire with the outlines mode- 

 rately curved : whorls eight, convex, with a well impressed 

 suture : aperture obliquely ovate, effuse above and below : 

 labrum moderately thickened, well excurved and produced 

 along the middle. 



Mean divergence about 33 ; length .13 inch ; breadth .05 

 inch ; length of spire .08 inch. 



/Station. Unknown. 



Habitat. Panama ; C. B. A. ! 

 1 specimen was found in sand. 



