146 



POPULAR CONCHOLOGY. 



Trochotom a conn lo ides 



the lip 



Trochotoma. Deslongchamp. (Ditremaria jD' Orb.) 

 — Shell with a slit on the outer lip, ap- 

 proaching the edge, but not reaching it; 

 the base has an umbilicus, and the aper- 

 ture is half-moon-shaped ; the outer lip is 

 a little thickened ; the whorls are usually 

 angular, and concentrically striped. — 

 Fossil. 



Very like Trochus in form, but the slit near 

 distinguishes it. Only known in the fossil state. 



Cirrus. Sow. — Shell spiral, conical, with a hollow 

 axis ; whorls contiguous, numerous, 

 rounded, or slightly angulated. * — 

 Fossil. 



Sowerby observes that this fossil is 

 distinguished from Trochus by the 

 deep funnel-shaped umbilicus : seve- 

 ral species are represented in that 

 author's work called Mineral Concho- 

 logy. The name signifies a curl, the 

 form bearing some resemblance to one 

 mon in the white chalk. Philippi remarks that the 

 mouth is entire, but that there are at a short distance from 

 the margin, tube-like apertures as in Haliotis. 



Haliotis. Lin. — Shell 

 flat, ear-shaped, very pearly 

 inside ; aperture very large, 



Cirrus. 



they 



are corn- 



comprising very nearly the 

 whole of the shell ; outside 

 rough, slightly spiral at 

 one end, and having one 



Haliotis tuberculoid. 



* Sowerby's Genera of Shells. 



