342 NATICID^. 



and lines of growth ; whorls four, regularly convex ; sph^c mod- 

 erately elevated, blunt ; suture fine and deep, the edge of the wliorl 

 rising a little by the side of it ; sometimes one or two faint, 

 brownish Viands may be seen on the lower whorl ; ajierturc 

 ovate, more than lialf the length of the shell ; outer lip thin 

 and sharp ; inner margin thick, the callus white, abundant, 

 and pressed into the umbilicus so as to leave only a narrow, 

 curved chink ])y the side of the lip ; throat white ; opercu- 

 lum horny. Length, half an incli ; breadth, four fifths of an inch. 



Taken from fishes caught in Massachusetts Bay, in company with 

 Natica clausa and Mamma immaculata. 



Most of the specimens have about half the dimensions above 

 given. 



I was not a little gratified, in looking over a parcel of the Natica 

 clausa, to find several specimens differing from them in having a 

 horny instead of a bony operculum, a partial umbilicus, and no flat- 

 tening of the top of the whorls. In color, size, and general aspect 

 they were the same. On finding that this shell corresponds to Mr. 

 Say's* Natica piisilla, I was still more gratified, inasmuch as it is 

 represented in the cabinet of the Academy of Natural Sciences, at 

 Philadelphia, by a species of Margarita (^Turbo inflates, Totten), 

 and I had despaired of finding any representative elsewhere. Mr. 

 Say remarks, that it is generally mistaken for the young of N. du- 

 plicata. But the evidences of maturity in its callus, the umbilicus, 

 and the color of the throat, sufficiently distinguish it from both 

 Neverita diiplicata and Lunatia heros. 

 Grand Manan to Cape Cod (Stimpson). 



Genus NATICA, Adanson. 1757. 



Operculum horny, with a calcareous outer layer. 



Shell sub-globose ; spire rather elevated ; aperture semi-lunar ; 

 columella adherent to, and spirally contorted in, the umbilicus ; 

 apex more or less dilated and truncate, more rarely convex or 

 rounded. 



Natica clausa. 



Fig. 167. 



Shell sub-globose, more or less tinged with brown; umbihcus closed; opercu- 

 lum calcareous. 



* This is not Say's species. See Stimpson, Shells of New England, 1, c. — W. G. B. 



