TRIFORIS. 323 



tencd, traversed by immeroiis 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 <i;ran- ^. ,„, 



, , ~ Fig. 591. 



ules, 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 ; ^ f"^*"*""- 

 two black threads, emerging from the aperture, revolve around the 

 base of the shell ; suture distinctly marked ; aperture al)out one 

 eighth the length of the shell, nearly circular, terminating in a deep, 

 very short canal, partly closed over by the lips ; outer lip sliarp, 

 notched, and a little everted ; pillar twisted, regularly arched above. 

 Length, one fifth of an inch ; breadth, one twentieth of an inch ; 

 divergence, thirty-five degrees. 



Found l)y Professor Adams in Dartmouth Harbor, clinging to 

 marine plants, a few feet below low water, with other species. Bos- 

 ton Harlior, southwards ( Stimpson). 



This little shell would hardly be distinguished when mixed with 

 the young of B. iii<j;'nnii. Its color is the same, and it is not unlike 

 it in marking. From the full-grown shell it is readily distinguished 

 by its bulging shape, the apparent jutting of one whorl over an- 

 other, its smaller size, and by its deeply notched canal. 



Oeiitis TRIFORIS, Desh. 1825. 



Shell turreted, sinistral ; aperture round, produced anteriorly 

 into a closed, tubular canal, sometimes with a posterior, closed 

 canal. 



Triforis nigrocinctus. 



Fig. 182. 



Sliell small, redclish-bLack, granulated ; whorls twelve, reversed ; aperture 

 small ; beak short and recurved. 



Ceritldnm uigrorlnrium, Apaais, Bost. Journ. Nat. Hist. ii. 286, pi. 4, fig. H. — Gould, 



Inv. 1st cd. 277, fig. 182. 

 Triforis nigrocinctus, Stimpson, Check Lists, .5. 



Shell small, conico-cvlindrical, blackish-red, with three revolving 

 series of rounded, bead-like granules, formed by numerous ribs or 



