278 INVERTEBRATA OF MASSACHUSETTS. 



tagu, but is probably different, as that shell has the middle series 

 smaller, and the canal straight. It is also of a lighter color. 



The whole shell, when fresh, is of a uniform color, so that the dark 

 revolving line at the suture is scarcely distinguishable, instead of 

 something evident, as we should expect from the name. The specific 

 appellation, on this account, is not well chosen. In some lio-hter- 

 colored individuals, however, the zone is very apparent. 



Cerithium Sayi. 



Shell small, ashy or slate-colored, covered ivith a fine net-work 

 of elevated lines ; aperture rounded ; canal merely an oblique 

 fissure. 



Figure 183. 



State Coll., No. 278. Soc. Cab., No. 713. 



Cerithium reticulatum, Totten ; SUUmaii's Journ., xxviii. 352, fig. 8. 

 Pasithea nigra, Totten ; (the young ;) Sllliman's Journ., xxvi. 369, pi. 1, f. 7. 

 Cerithium Sayi, Menke. 



Shell small, elongated-conical, somewhat turreted, the upper 

 whorls of a blue-black or slate-color, and two or three of the 

 lower ones usually much lighter, white, or ashy gray ; whorls six 

 or eight, forming an elevated, conical spire ; surface covered with 

 a granular net- work from the crossing of slightly elevated, rounded 

 folds or ribs, and elevated spiral lines ; of the ribs there are about 

 twenty, which vanish on the lower half of the anterior whorl ; of 

 the spiral lines there are about six on the lower whorl but one, 

 five on the next above, and so on ; besides these, on the anterior 

 whorl are about six raised revolving lines about the base, par- 

 tially granulated ; suture distinct, with the series of granules next 

 below it rather largest, so as to form a slight shoulder ; aperture 

 oblique, rounded, and flaring, about one quarter the length of the 

 shell, broad anteriorly ; outer lip sharp, modified by the revolving 

 lines ; inner margin angular-concave, with a plate of enamel, 

 not pressed close upon the body whorl, uniting the two lips 

 above, and forming an umbilical fissure below ; canal a mere ob- 

 lique fissure or notch, not prolonged forward so far as the lip ; 

 operculum horny, ovate ; apex at the centre of the broader part, 

 concave outwardly, with four or five spiral turns. Length fV inch, 

 breadth yV inch, divergence 28°. 



