>.] 



117 • [Perkins. 



the centre of the top, a little below it, oval ; capsule colorless, trans- 

 parent, ova minute, white. Height two and three-fifths mill.: 

 breadth in the middle two and one-fifth mill. ; breadth of base one 

 mill. Laid in April and May. 



Nassa Lam., 1799. 



Nassa fretensis 1 nov. sp. 



Shell solid, short, obese, whorls six, undulated by prominent costae, 

 of which there are fifteen or sixteen on the body whorls and fewer on 

 the upper whorls, vanishing near the apex ; near the outer lip they 

 are wanting, or quite faint; on the lower part of the body whorl the 

 costae are nearly straight and oblique ; near the suture they make an 

 angle bending towards the left ; the costse are cancellated by ten or 

 twelve elevated lines ; suture distinct ; whorls slightly shouldered ; 

 aperture oval ; lip much thickened by a large varix, and 

 toothed within by about four lamellar teeth ; pillar lip 

 arched by a moderately thick callus, which scarcely ex- 

 tends above the aperture, and bears inside near the top 

 a single tubercle; spire short, conical; canal very short, 

 curved ; color dark purplish brown with a yellowish band 

 around the upper part of the body whorl, which is continued around 

 the middle of the upper whorls ; terminal whorls and upper part of 

 the lip and lower half of the columella greenish yellow; interior 

 usually purplish brown. Length fifteen mill. (.6 in.) ; breadth ten 

 mill. (.4 in.). Not common. This shell has heretofore undoubtedly 

 been confounded with Nassa vibex Say, which it resembles ; but the 

 spire is less acute, its ribs more numerous and narrower, its revolving 

 lines more prominent, the callus much thinner and smaller, and the 

 color much darker. It has also been found near Salem, Mass. 



. CERITHIOPSIDiE. 



Cerithiopsis Forbes and Hanley, 1849. 



Cerithiopsis Emersoni Stimps., Check List. Cerithium Emer- 

 soni Gould, Invert. Mass., p. 275, fig. 180; De Kay, Moll. N. Y., p. 

 129, pi. viii,fig. 168. 



Very rare ; only dead shells were found. 



1 Fretum, a sound, and ensis, locative ending. 



