RissoA. Panama Shells. 177 



remote a latitude as Chiloe. Dr. Ptilippi has, therefore, with 

 much reason, quoted with doubt the statement of M. Petit, 



243. Rissoa clandcstina. Nov. sp. 



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

 about eighteen or nineteen stout prominent compressed ribsj 

 which are continued to the anterior extremity: apex acute: 

 Bpire with the outlines moderately curvilinear : whorls seven, 

 Inoderately convex : with a well impressed suture : last whorl 

 rather large : aperture large, oblique, moderately effuse at both 

 extremities: labrum much advanced along the middle, much 

 thickened with a broad varix : umbilicus wanting. 



Mean divergence about 30° ; length .115 inch ; breadth .05 

 inch ; length of spire .07 inch. 



Station. — Unknown. 



Habitat. — Panama ; 0. B. A. 1 

 2 specimens were found. 



244. Rissoa firmata. Nov. sp. 



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

 about twelve very stout, prominent, rather acute ribs, which 

 are continued to the anterior extremity : apex acute : spire with 

 the outlines curvilinear: whorls seven, convex, with a well 

 impressed suture: last whorl rather large: aperture oblique, 

 BuboVate, effuse at both extremities: labrum well advanced 

 along the middle, thickened with a broad stout rib : umbilicus 

 wanting. 



Mean divergence about 30° ; length .185 inch ; breadth .075 

 inch ; length of spire .18 inch. 



Station. — Unknown. 



Eaiitat. — Panama ; 0. B. A. I 



1 specimen was found in the sand. 



JULY, 1853. 46 Ami. Ltc. Nat. Hwt. 



