72 Monograph on the C^prceidece, bj/ Mr. Gray. 



longitudinal comb-like series on the inside of the columella or left 

 side of the mantle, edge of the mantle forming a short siphon 

 at each end of the aperture of the shell. 



Mantle, edges enlarged, wing-like, reflected over the back of 

 the shell and depositing its last coats, the lines of union of the 

 refiexed portions forming the dorsal line of the shell. 



Ventral disk or iwcArer tongue-shaped, adductor muscle attached 

 to the columella. Operculum, none. 



SuELL, oval or oblong, becoming covered with a fine, shelly, 

 highly polished, or variously striated coat, deposited by the re- 

 flexed lobes of the mantle, leaving a dorsal line or groove. 



Shelly cone, whorls very rapidly enlarging, revolving nearly on 

 the same plane, so as to exhibit none, or only a small, concave, 

 flat or convex spire. 



Aperture longitudinal, with a channel or groove at each end. 

 Inner lip flattened or rather concave in front, smooth or be- 

 coming plaited, outer lip becoming involute, thickened, plaited. 



The shell alters its appearance considerably, according to the 

 age of the individual, and exhibits three very distinct stages. In 

 the young or first stages, which are figured in Ency. Method.t. 349, 

 f. a. b. Mus. Gotwald, viii. t. 53, b. e. 65, a.f. 66, a. c. the 

 shell is generally smooth, of a plain greyish colour, or with three 

 longitudinal bands, and the upper part of the inner lip is smootli, 

 convex, the lower part flat or concave ; the outer lip thin. In 

 the second stage, the shell begins to assume more the character 

 of the genus, as the outer lip begins to be inflected or rather thick- 

 ened, and approaches nearer the perfect appearance of the species 

 as the second coat of colour is deposited ; but difters from it in 

 the want of thickness of the shell and the spire being more dis- 

 tinct, and in the want of the dorsal line, which is usually distinct 

 in the third or perfect state, where the last coat has been de- 

 posited, and the aperture is more plaited on both sides. 



The colouring, or at least, the disposition of the colouring here, 

 is a much more certain characteristic of species, than either the 

 general outline of form or size, the latter of which is exceedingly 

 various. In this family 1 have often observed full-grown speci- 

 picns of C. arabica from one to three inches long ; this peculiarity 



