Fain. 60.] NATURAL HISTORY SOCIETY. 141 



short stout tentacles and es^es on their outer bases ; foot very 

 short, indented in front and rounded behind. 



1. Seila ierebralis, C. B. Ad. Shell long, conical; whorls flat- 

 tened, with 3 or 4 revolving ridges on each, and numerous, fine, 

 longitudinal lines between them ; aperture oval ; base abrupt. 

 Reddish-brown. L. 12; D. 3; An. 18°; Wh. 10-12; Ap. f — 

 Mass. 



2. Cerithiopsis, Forbes and Hanly. 



Shell nearly as in Seila; operculum paucispiral, somewhat 

 concave, smooth outside, of 3 or 4 whorls. Animal with foot 

 and tentacles much more elongated than in Seila. 



1. Cerithiojms Greenii, C. B. Ad. Shell conic-cylindrical, with 

 20-25, slightly elevated ribs on the body whorl, and crossed by 

 3, revolving, impressed lines on nearly all the whorls, forming 

 three series of granules ; aperture nearly circular ; canal short 

 and deep. Reddish-black. L. 5; D. IJ; An. 30°; Wh. 10-12; 

 Ap. f. Mass. and south. 



2. Ceritkioims suhidata, Montagu. Shell long, conical ; whorls 

 dat, each with three rows of granules ; suture very deeply im- 

 pressed ; aperture subquadrate ; canal less than |^ the length of 

 the aperture, columella twisted. Color dark reddish-brown. 

 Animal with a long, small foot, truncate in front, and notched 

 behind ; very light colored, with flecks of opaque white, h. 13 ; 

 D. 3; An. 20°; Wh. 17; Ap. J.— New England. 



Family 60. CERITHIID/E. 

 .Shells very similar to those of the preceeding family, but the 

 proboscis of the animal is only contractile instead of being re- 

 tractile. 



1. BiTTiUM, Leach. 



Shell elevated, with numerous granulated whorls and irregular 

 varices ; anterior canal short and not recurved ; outer lip not re* 

 curved ; operculum 4 whorled. 



1. Bittium alternatum, Say. Shell acute, conic, thin ; whorls 

 with a distinct shoulder formed by a series of granules ; surface 

 granular from the crossing of slightly elevated ribs and spiral 

 lines ; the ribs, about 20 in number, disappear on the lower half 

 of the body-whorl, leaving there about 6, elevated, revolving 

 lines ; suture deeply impressed ; lip sharp, modified by the re- 



