190 POPULAR BRITISH CONCHOLOGY. 



It appears from this account^ that the epidermis of the 

 mussel affords a great protection against marine animals of 

 predaceous habits, for a fine specimen with that covering 

 perfect would hardly be attacked. This is Nature's method 

 of preventing the too rapid diminution in the number of a 

 species of acknowledged utility to man. 



IV. Nassa. — This genus contains numerous small species 

 of mollusca formerly mixed up with the genus Buccinum. 

 The shells are much smaller, but have a similarly ribbed 

 and furrowed spiral character ; their spire is generally co- 

 nical, and the last whorl moderately large, toothed, and ter- 

 minating in a short but strongly-marked canal; a distin- 

 guishing character of Nassa is that the inner lip ends in a 

 little knob, with a notch beneath it. The animal has a large 

 foot, with a fork at the hinder end, and a kind of hook at 

 each corner of the truncated front ; the operculum is small, 

 pear-shaped, and very pointed; the eyes are on swellings 

 about one-third up the pointed tentacles. These lively 

 little creatures move about freely in rather shallow water, 

 using their retractile proboscis with fatal effect on the vic- 

 tims devoted to their appetites. The mantle is produced 

 in front into a siphonal tube, pushed out far beyond the 

 canal of the shell. The young Nassa are deposited in small 

 membranous capsules. The British species are — 



