FAMILY CERITHID^ CERITHIUM. 129 



elevated folds with elevated spiral lines : about twenty of these ribs, which disappear on the 

 lower half of the body-whorl, leaving there only about six slightly elevated revolving lines. 

 Suture deeply impressed. Aperture about a fourth of the length of the shell, elongate, sub- 

 ovate, acutely angular above, widely rounded below, slightly effuse. Lip sharp, modified by 

 the revolving hnes ; the canal, if it can be said to exist, is a mere oblique fissure. Opercle 

 horny, ovate, concave externally, mullispiral. 



Color. Bluish black to reddish black. 



Length, 0-2 -0-3. Width,0-1. 



This species was first described by Col. Totten, from immature specimens, and referred 

 to Pasithea. The subsequent acquisition of full grown shells enabled him to refer it to the 

 present genus, where, however, it is not likely long to remain. The imperfect development 

 of the canal may probably induce some writers to refer it to Potamida of Brongniart, or to 

 construct a new and closely allied genus. 



This shell is common on the shores of this State. In some specimens collected by Dr. 

 Stillman, the upper whorls are blackish, and furnislied with distinct vertical elevated lines ; 

 on the three lower whorls, the revolving lines are very distinct, the color light brown, with 

 rufous elevated vertical lines. 



{EXTRA-LIMITAL) 



C. ferrugineum. (Say, Am. Conch, pi. 49, fig. 3.) Whorls 7, with longitudinal ribs, rendered no- 

 dulous by spiral striae. About 20 ribs on the body-whorl, almost interrupted by the interstices of 

 the strife. Stris 7 on the body-whorl, with intermediate smaller ones ; 3 on the second whorl : 

 suture not very distinct. Aperture oblique, oval ; lip somewhat thickened on the outer margin. 

 Color, ferruginous; within whitish. Florida. 



C. emerso7iii. (Adams, Bost. Jour. Vol. 2, p. 284, pi. 4, fig. 10. Gould, fig. 180. Pl. 8, fig. 168 of 

 this book.) Shell long, conical: whorls 17, flat, each with three rows of granules ; suture very 

 deeply impressed ; aperture small, subquadrate, about one-sixth the length of the shell ; columella 

 spirally twisted ; canal less than half the length of the aperture. Color, dark reddish brown. 

 Length, 0-5; width, 0- 12. Nantucket. 



C. septemstriatum. (Say, Am. Conchol. pl. 49.) Shell turreted, with ribs made somewhat nodulous 

 by elevated spiral strios. Ribs about 13 on the body-whorl, bifid towards the base. Spiral stria; 7 

 on the body-whorl, 7 on the second, and 3 on the third: volutions 9. Color, dusky or blackish; 

 the interstices of the stri» often whitish. Lip whitish, often interrupted by small brown lines. 

 Florida. 



C. nigrocinctum. (Adams, 1. c. Vol. 2, p. 286, pl. 4, fig. 11.) Shell small, conic-cyHndrical, with 

 3 revolving series of granules. Whorls reversed or heterostrophe ; suture broad, carinate ; aper- 

 ture small, subelliptical, ending in a twisted canal about one-third as long as the aperture. Color, 

 reddish black ; columella black ; a black spiral bek in faded shells. Length, 0-3; width, 0-07. 

 Massachusetts. 

 Fauna — Part 6. 17 



