CANALIFERA. MOLLUSCA. CERITHIUM. 279 



Found very abundantly at Nantucket, Martha's Vineyard, New 

 Bedford, &c. It has not been found to my knowledge within, or 

 to the north of, Cape Cod. Its proper station is on sea-weed, 

 stones, and marine bodies, about low-water mark. The young are 

 sometimes seen in such numbers as to conceal the sand beneath 

 them. These are always reddish-black, with a very different 

 aperture. It seems not to attain its growth the first season, and 

 the second year's growth is usually distinctly indicated by its 

 much lighter color. 



The name given by Colonel Totten, at my suggestion, is pre- 

 occupied by an English species. Its wide expanded mouth, with 

 scarcely any thing like a canal, renders its claim to a place in the 

 genus Ceri'thium rather equivocal. These characters, with its sculp- 

 ture, distinguish the species. 



Ceri'thium Gre'enii. 



Shell small, reddish-black, tumido-conic, elongated, tcith longi- 

 tudinal ridges and revolving lines ; canal very deep and very shorty 

 slightly curved. 



Figure 184. 



State Coll., No. 277. Soc. Cab., No. 2362. 



Cerithium Greenii, Adams ; Bosf. Journ. J\'at. Hist., ii. 287, pi. 4, f. 12. 



Shell small, elevated-conic, sloping somewhat abruptly above 

 the middle, to a prolonged, pointed apex ; whorls ten or twelve, 

 flattened, traversed by numerous folds or ridges, of which there 

 are from twenty to twenty-five on the lower whorl, crossed by three 

 revolving impressed lines, producing three series of granules, of 

 which the lower one is largest, so that the base of each whorl 

 seems to jut over the one below it ; the upper series is nearer to 

 the middle one than that is to the lower one, and soon disappears 

 on the upper whorls ; then the middle one vanishes, and finally the 

 lower one, so that the whorls at the apex are either smooth or 

 merely wrinkled ; two black threads, emerging from the aperture, 

 revolve around the base of the shell ; suture distinctly marked ; 

 aperture about one eighth the length of the shell, nearly circular, 

 terminating in a deep, very short canal, partly closed over by the 



