136 NEW-YORK FAUNA — MOLLUSCA. 



Purpura imbricata. 



PLATE VIII. FIG. 173. 



Pitrpura imhricaia, Lam. An. sans verl^bres, Ed. prior, Vol. 7, p. 244. 

 P. lapiUus, vdr. RussEL, Op. cit. VoU 1 , p, 70. Godld, Op. cit. p. 302. 



Description. Shell resembling the preceding in configuration, but more dilated, and not as 

 solid : the spire more rapidly attenuated to the apex ; the revolving ribs are more numerous, 

 and rather more distinct ; the ribs crossed by numerous waved imbricated scales, extending 

 to the apex. Suture deep : whorls more convex ; columella with a broad callus, and its base 

 shorter and broader than in the preceding ; lip much rounded, expanded, and crenulated on 

 the margin. 



Color. Greenish or greenish mixed with grey. 



Length, 0-7 -1-0; of aperture, 0-5 -0-7. 



Occurs with the preceding. Lamarck observes that it may be only a variety of the pre- 

 ceding, but that it differs eminently by the imbricated scales, which render it rough to the 

 touch. 



Purpura bizonalis. 



PLATE Vm. FIG. 174. 



Ptajmra bizojialis, Lamarck, An. sans vert. Ed. prior. Vol. 7, p. 249. 

 P. lapillas, var. Gofld, Invertebrata of Mass. p. 303. 



Description. Shell rather smaller than the two preceding, solid : spire short, acute. Whorls 

 four to five, with moderate revolving ribs on all except the apicial ones, which are smooth : 

 body-whorl dilated ; lip not crenate ; base of the columella short, emarginate at its junction 

 with the lip : canal obsolete. 



Color. Chocolate-brown, with two revolving white bands, which are most evident on the 

 body-whorl ; the upper band broadest. 



Length, 0-5 - 0*6. 



Occurs with the preceding, but is more rare. In old specimens, the ribs are strongly 

 impressed by the incremental lines. 



(EXTRALIMITAL.) 



P.floridana. (Conrad, Ac. Sc. Vol.7, p. 265, pi. 20, fig. 21.) Shell fusiform; whorls slightly 

 concave above ; spiral strise prominent, unequal. Whorls angular, with a series of tubercles on 

 the angle ; those of the spire longitudinally phcate ; two terminal whorls smooth : lip thin, furrowed 

 within on the margin. Color, varied white and brown ; occasionally series of narrow pale stripes 

 with brown spots. Florida, Alabama. 



