MARINE MOLLUSCA OF THE UNITED STATES. 33 



callosity or blunt dentiform plait; outer lip dentated, internally 

 crenulated. Operculum ovate, the margin serrated or entire. 

 Eyes on the middle of the tentacles. Foot large, expanded, fre- 

 quently bifurcate at its posterior extremity. 



The animal is exceedingly active in its movements, feeding on 

 bivalves, which it pierces with its proboscis, extracting the con- 

 tents through a small, round aperture. There are over two hun- 

 dred species, of world-wide distribution; ranging from low water 

 to fifty fathoms. 



1. N. obsoleta, Say. Figs. 48, 49, and 50. 



Journ. Philad. Acad. Nat. Sciences, ii. 232. 1822. 



Ilyanassa obsoleta, Stimpson, Am. Journ. Conch., i. 61. 1865. 

 Buccinum Nov-Eboracensis, Wood, Index Test, Suppl., t. 4, f. 26. 

 Buccinum olioiforme, Kiener, Iconog., t. 25, f. 99. 



Shell ovate, solid; apex eroded; spire short; whorls six, flat- 

 tened, convex, reticulated, the ridges flattened ; aperture rather 

 less than half the total length of the shell, outer lip simple, stri- 

 ated within. Dark reddish-brown, purplish within, with frequently 

 a white revolving band. Operculum obovate, broadest below; 

 nucleus a little within the margin at the outer side near the base; 

 margin entire, not serrated. 



Animal variously mottled with slate-color; foot as long as the 

 shell, its' anterior angles prolonged and turned backwards, and 

 without caudal bifurcation ; head not extending beyond the shell ; 

 eyes black, on the exterior side of the tentacula, and above the 

 base ; above the eyes the tentacula are suddenly diminished and 

 bristle-shaped ; proboscis cylindrical, half the length of the shell, 

 channelled beneath. 



Ova-capsules (fig. 50) rounded, erect, slightly compressed, with 

 the anterior and upper surface covered with facettes formed by 

 reticulating ridges or crests, the angles of which are spinous. 



This is the type of Stimpson's genus Ilyanasa, differing from 

 the typical Nassse in the form of the operculum and the want of 

 caudal bifurcation. 



Littoral, living on mud-flats in bays and harbors ; ver} T abun- 

 dant. 



Entire Coast from Maine to Florida. 



2. N. trivittata, Say. Fig. 51. 



Journ. Philad. Acad. Nat. Sc, ii. 231. 1822. 



Shell robust, ovate-conic; spire elevated, acute, longer than the 

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