346 



NATICIDj;. 



N. diipticata. 



behind by a very small angle, but this angle is so filled 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, gen- 

 erally 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 ; opercu- 

 lum horny. Length, two inches ; 

 breadth, rather more. 



Inhabits the same localities as 

 Limatia heros ; is less common in 

 the vicinity of Boston, but com- 

 mon at Nantucket. Charleston, 

 South Carolina (^Stimpson) ; mouth of Rio Grande {ScIioW). 



This species is subject to considerable variation in shape, some 

 individuals 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 sliell. Specimens 

 along the Southern coast are generally less elevated, more smooth 

 and Ijrown than those found in Massachusetts. I have a specimen 

 from the Grecian island, Syra, which corresponds with these, ex- 

 cept that the colors are brighter, and the shell more sinooth, as 

 miglit 1)6 expected if modified by a milder climate. A figure in 

 Lister (pi. 562, fig. 3), represents this shell. 



Natica conica, of Lamarck, is a much more elevated shell, though 

 his description might be applied to our shell in every particular. 

 Its ordinary length is half an inch less than is given above. 

 [Foot sub-rhomboidal, rounded before as behind, where it is 

 broader than before ; broadest about the middle, across the shell ; 

 anteriorly light-fawn, posteriorly dark gray, especially at margins ; 

 mentum dark gray anteriorly, becoming lighter posteriorly, forming 

 a prominent dark-edged siphon at left side, reflection nearly cover- 

 ing shell ; beneath wine-yellow ; scissure across foot just in front of 

 broadest part extending forward to a point at middle ; tentacles 

 vertically compressed, pyramidal, with maculations on a pale ground, 

 with a narrow black margin each side to point; a flattened lobe at 

 base outside; no eyes. (^Stimpson.} 



