236 INVERTEBRATA OF MASSACHUSETTS. 



Ampulla RiA, but the operculum of Na'tica. A specimen sent to mc 

 by Dr. Loven was regarded by him as new, and he had applied to it 

 the name of N. exulans. 



Natica duplicata. 



Shell conical-ovate, usually with a dark band above the suture 

 on the upper ivhorls ; umbilicus deeply grooved, and partially or 

 entirely covered xoith a chestnut-colored callus. 



Figures 163, 164. 



State Coll., No. 58. Society's Coll., No. 78. 



Natica duplicata, Say ; Journ. Acad. JVat. Sc, ii. 247. 



Shell solid, ovate, the upper portion of the whorls compressed 

 so as to give it a pyramidal outline ; surface marked with very 

 faint revolving lines, and more conspicuous lines of growth ; color 

 light chestnut-brown above a line marking its greatest circumfer- 

 ence, whitish or ash-colored below it ; usually having a dark-brown 

 band on the lower portion of the posterior whorls, and the upper 

 portion whitish ; whorls five or more, spire rather prominent ; 

 aperture ovate, very oblique ; outer lip very thin and sharp, join- 

 ing the whorl behind by a very small angle, but this angle is so 

 fiilled up within with callus, that the real aperture is rounded, and 

 at a considerable distance from the junction of the lip ; throat 

 chestnut-brown, or livid, lower portion white, generally of a 

 pearly lustre ; umbilicus irregular, having a deep groove revolving 

 within it, and covered wholly or partly with a very thick, chestnut- 

 brown callus ; operculum horny. Length 2 inches, breadth rather 

 more. 



Inhabits the same localities as N. heros ; is less common in the 

 vicinity of Boston, but common at Nantucket. 



This species is subject to considerable variation in shape, some in- 

 dividuals having the spire much more elevated than others. It is 

 easily distinguished by its conical figure, and by the great amount of 

 callus, which renders it a remarkably heavy shell. Specimens along 

 the Southern coast are generally less elevated, more smooth and brown 

 than those found in Massachusetts. I have a specimen from the Grecian 

 island, Syra, wliich corresponds with these, except that the colors are 



