390 



MARINE INVERTEBRATES 



FAMILY NASSIDJE 



These are familiar, and often very characteristic, littoral shells 

 in all parts of the world. Where they exist at all they are gener- 

 ally to be found in astonishingly large numbers, sometimes even 

 crowding out all other mollusks. They are exceedingly active 

 and predaceous, feeding upon other mollusks, whose shells they 

 bore through by means of the sharp teeth upon their lingual 

 ribbon. The Nassidce of the east coast find a relentless enemy 

 in the small hermit-crabs, which attack them, drag them from 

 their coverings, and then proceed to occupy the empty shells 

 themselves; the torn and lacerated Nassa animal is thereupon 

 leisurely eaten, a retribution probably well deserved. The animal 

 of Nassa (the principal genus of Nassidte) is peculiar in having 

 frequently a bifurcated tail; or, to speak more correctly, the 

 posterior end of the foot is terminated by two appendices. 

 It has a long siphon, and eyes placed upon the outer sides and 

 near the base of the tentacles. The operculum has serrated 

 edges. 



GENUS Nassa 



N. trivittata, N. obsoleta. These are the two nassas of the New 

 England and New Jersey coasts. The first has a more northerly range, 



extending to the Gulf of 

 St. Lawrence ; the other is 

 not usually found north 

 of Cape Cod, but below 

 that point as far as Hat- 

 teras it is probably the 

 commonest shell of the 



NOSM trivittata. showing the animal as if crawling. COast. It fairly S warm S in 



sheltered muddy reaches 



about low tide. Little pools left by the tide on the Jersey 

 flats are sometimes so crowded with N. obsoleta that for lack 

 of room the animals crawl over one another. N. trivittata is 

 more commonly taken at small depths in the harbors, where 

 it seems to live well upon all kinds of sea-bottom. Probably 

 they exist in great numbers along the southern shore of Long 

 Island, for the beaches are often lined with their dead and 

 worn shells. Over half the specimens thus found will have a 

 little round perforation upon some whorl, showing that they 

 were victims of some cannibalistic brother. The shells of the 

 Nassidas have a short, ovate aperture, with a short anterior canal. The 

 inner Up is smooth, and is usually coated over with a more or less heavy 



