72 TRACHELIPODA. 



Genus 20.— RlCllSl U LA. —Lamarck. 



Generic Character. — Shell ovate, usually tubercular or spinous 

 externally ; aperture longitudinal, furnished with a short re- 

 curvate canal, terminated by an oblique notch ; columella with 

 unequal teeth ; the interior of the right lip frequently obtruding 

 on the aperture. 



Ricinula horrida. —The Rugged Ricinula. Plate XL fig. 

 20. External surface covered with strong, obtuse, black tuber- 

 cles ; the interstices being white and transversely striated ; inside 

 of both lips of a rich purple ; outer lip with five triangular, 

 grooved radii, between which, at their base, the margin is crenu- 

 lated. One and a-half inch long. Inhabits the East Indian 

 seas. 



Genus 21. — CASSIS. — Lamarck. 



Generic Character. — Shell gibbous ; aperture longitudinal, 

 narrow, terminating in a short canal, abruptly reflected back- 

 wards ; columella transversely plicated or rugose ; outer lip 

 usually dentated. 



The genus consists of two subdivisions : 1. Spire with longi- 

 tudinal 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— CASSID ARIA.— Lamarck. 



Generic Qiaracter. — 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 the Cassis by the canal being ascendant, and very lit- 

 tle arched, and not suddenly recurved towards the back, as in that genus. 



Cassidaria Thyrrena. — The Thyrean Cassidaria. Plate 



