NASSA. 17 



(icnus NASSA, Lit m. 



H. and A. Adams in their "Genera of Recent Mollusca" have 

 enumerated' 210 species of Nassa; Reeve's Monograph in the 

 "Conchologia Iconica" contains 182 accepted species and 13 

 synonyms, = 195 names in all. The present monograph includes 

 595 specific names, of which 131 only are accepted as good 

 species, 364 are relegated to the synonymy of these, and 100 are 

 undetermined for want of illustrations or specimens. The dis- 

 tribution of the genus is world-wide, except that no specimens 

 exist in the icy seas near the poles- where they appear to be 

 replaced by the Buccinums. They occur principally in the waters 

 of tropical and subtropical latitudes. 



The fossil species are few in number, commencing with the 

 Eocene formation. For some of the American fossils Mr. T. A. 

 Conrad has proposed distinct generic names, but their separation 

 from Nassa is scarcely advisable. 



The animal of Nassa has a broad head, and a foot quadrately 

 expanded in front, with the corners often pointed, whilst behind 

 it bifurcates and is prolonged frequently into two subulate tails. 

 The operculum is usually serrate on the margin but is sometimes 

 plain. The Nassae are very active, and not at all shy when kept 

 in confinement. They may be occasionally seen floating with 

 the foot upwards. They are predaceous, feeding on other mol- 

 lusks, the shells of which they bore. I have frequently seen the 

 shells of the American species themselves bored, the hole being 

 of such a size as to suggest cannibalism. Perhaps the avenger 

 of their misdeeds is a beautiful and very active hermit crab 

 which disports itself in the Nassa's shell, immense multitudes 

 being seen at low tide in the water near the shore line. Whether 

 begged, borrowed, stolen, or lawfully captured by the red right 

 claw, it is certain that, at Atlantic City, New Jersey, the hermit 

 inhabits a vast majority of the specimens of Nassa occurring to 

 the collector. Although most of the species are littoral, a few 

 have been collected at considerable depths; the nndescribed N. 

 brycliia, Watson, was dredged at 620 fathoms by the " Challenger 

 Expedition." Some of them have been observed to spring 

 up and throw themselves over 011 being suddenly disturbed. 

 Usually they glide along the surface of the mud, leaving a track 

 indicating their line of march, at the end of which is a small 

 3 



