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MOLLUSC A. 87 



rough shells, with ridges, spines, or tubercles, which are secreted periodi- 

 cally, in three or four rows around the shell. The right margin of the 

 mantle is divided into lobes, the irregularities of which account for those 

 of the shell in the difi'erent species. There are about 170 recent and 130 

 tertiary fossil species known. 



Harjxt {H. ventrlcosa^ j)l- ^^^ifiQ- ^l^) is a genus of finely formed ribbed 

 shells of brilliant colors, and a polished exterior. The foot is very large, 

 and without an operculum. Ten species are described in Lamarck. The 

 genus occurs fossil in the Paris basin. 



Cassidaria {C. echinophora^ pi. 75,Jifjf. 121). This genus contains a few 

 recent and fossil S2)ecies. The animal is like that of Cassis, in which the 

 foot is longer than the shell, tlie head proboscidiform, with a projecting 

 rostrum and mouth from its extremity. 



Fusus is a genus of marine shells, thickest in the middle, and tapering 

 towards both ends ; the animal with a small head, ending in two short 

 tentacles, the eyes at their external base, but not upon a peduncle or 

 thickening of the tentacle, thus differing from Murex and Purpura, but 

 allied to Turbinella and Fasciolaria. The head has a terminal slit, whence 

 the rostrum issues, and the nucleus of the operculum is terminal. 



Fmn. 8. Strombidce. In this family the right margin of the aperture is 

 dilated, corresponding to the wndth of the mantle, but this character is not 

 present in the immature shells, so that a young Stromhus {pi. 75, Jig. 114) 

 might be mistaken for a Conus {p)l.''iQ,fig. 11). The head is proboscidi- 

 form, with a vertical slit from which a long rostrum is extended ; the 

 tentacles are large, divided at the end, and the truncated extremity of the 

 larger external branch bears the large eyes, which have a variously colored 

 iris and a cornea, which have not been observed in any of the allied 

 families. They live on coral banks at no great depth, and some species 

 attain to a considerable size. The locomotion differs from that of most 

 gastropoda, being effected by leaping, for wdiich purpose the operculum 

 (which has a peculiar shape) is applied to the ground. Strombus lentigi- 

 nosus {pi. 75, Jig. ll-l). S. gigas of the Antilles is eight or ten inches 

 long, and remarkable for the fine peach blossom tint of the aperture. The 

 shell is used to ornament grottoes and gardens, and by sawing off the apex 

 it is converted into a rude trumpet. Pterocera {P. Gldragra,pl.75, jig. 

 115) difl'ers from Strombus in having the adult shell digitated, and the struc- 

 ture of the mantle corresponding with it. Postellaria {B.7'edirostns,Jig. 116). 



P'iwi. 9. Conidw. The shell of the genus Conus {pi. 7^, Jigs. 8-12) is 

 obconical, involute, and has a short spire and a narrow aperture as long as 

 the body whirl ; and the exterior is covered with a periostraca. The genus 

 includes many beautiful and highly prized species. Linnceus described 35 

 species, Bruguieres 146, Lamarck 181, increased to 219 in the last edition 

 of 1845, exclusive of 23 European fossil species. At present there are 

 probably 300 recent species known. The head is proboscidiform, the eyes 

 are upon the middle of the tentacles, the foot is long and very narrow, 

 having a corneous sub-spiral operculum, so small in comparison with the 

 aperture, that it cannot serve to close the shell. The mantle is scanty (in 



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