84 TRACHELIPODA. 



five triangular, grooved rays, between which, at their base, 

 the margin is crenulated. One and a half inch long. In- 

 habits the East Indian seas. 



Genus 21.— CASSIS.— Lamarck. 



Generic Character. — Shell gibbous ; aperture longitudi- 

 nal, narrow, terminating in a short canal, abruptly reflected 

 backwards; columella transversely plicated or rugose; outer 

 lip usually dentated. 



The genus consists of two subdivisions: 1. Spire with 

 longitudinal varices. 2. Spire without varices. 



Cassis Areola. — The Patched Cassis. Plate XI. fig. 

 21. Smooth, shining, white, with square orange tesselated 

 spots ; spire short and conical, with decussated striae ; lower 

 part of columella rugose. Two and a half inches long. 

 Inhabits the Indian ocean. 



Genus 22.— CAS SID ARIA Lamarck. 



Generic Character. — Shell obovate, or ovate-oblong ; 

 aperture longitudinal, narrow, terminating in an ascending 

 curved canal ; outer lip marginated, or folded back at the 

 margin ; inner lip covering the columella, generally rough, 

 granular, tuberculate, or rugose. 



Distinguished from Cassis by the canal being ascendent, and very 

 little arched, and not suddenly recurved towards the back, as in that 

 genus. 



Cassidaria Thyrrena. — The Tyrrhene Cassidaria. 

 Plate XI. fig. 22. Ovate, transversely grooved, reddish 

 fulvous ; volutions convex ; the last turn generally with 

 one tuberculate groove ; aperture white ; columella rugosely 

 tuberculate. Three inches and a half long. Inhabits the 

 Mediterranean sea. 



FAMILY IV. ALATA. 



Shell provided with a canal of greater or less extent, at 

 the base of the aperture ; the right lip changing its form as 



