Fam. o4.] NATUKAL HISTOKY SOCIETY. 135 



ly crenulated with a few small teeth at some distance from the 

 'edge. Animal with a broad head, and a foot notched behind,, 

 and often prolonged into two subulate tails. These animals are 

 very active, and not at all shy when kept in confinement. 



1. Nassa ohsoleta, Say. (Fig. 45). Shell solid; apex eroded; 

 spire short; whorls flattened convex ; surface covered with 

 numerous, unequal revolving lines which are crossed by numer- 

 ous oblique folds, giving the surface, when the greenish, mould- 

 like plants are removed, a reticulated appearance. Dark reddish- 

 brown, purplish within. Animal mottled with slate-color ; foot 

 equal to the shell in length. L. 25 ; D. 12; An. 55°; Wh. 6; Ap. 

 ^. — Whole coast. Very abundant on mud flats. 



2. Nassa triviiiata, Say. (Fig. 36). Spire elevated, acute; 

 whorls flattened, and with a conspicuous shoulder at the suture ; 

 whole surface covered with a network of granules formed by 

 revolving lines and ribs ; about 10 revolving lines on the body 

 whorl. Greenish or yellowish-white, sometimes banded on body 

 whorl. Animal whitish, sparsely dotted with pale lilac. L. 18 ; 

 D. 8 ; An. 45° ; Wh. 7 ; Ap. |.— Whole coast. Common. 



3. Nassa vihex, Say. Shell thick, ovate-conic; spire short, 

 acute ; body whorl witn from 10-12 undulating ribs which are 

 continued to tlie apex, and about the same number of revolving 

 lines which are most distinct on the ribs ; outer lip thickened and 

 with 2-5 teeth within; pillar very concave, and with much 

 callus. Color ashy- white to pale reddish -brown, with darker 

 revolving bands. Animal about J longer than shell, light colored, 

 and mottled. L. 13 ; D. 8 ; An. 67° ; Wh. 6 ; Ap. §.— Cape Cod 

 and south. Rather rare. 



Family 54. COLUMBELLID/E. 



Shell oval, covered with an epidermis; spire generally short; 



aperture narrow, elongated, ending in a very short anterior canal, 



inner lip usually dentate; outer lip generally thick. Animal 



with a large flattened head ; foot narrow ; operculum very small. 



1. CoLUMBELLA, Lam. 



Shell elongated ; aperture narrow, with a short, anterior canal ; 

 inner lip, crenulated to smooth ; outer lip inflected, internally 

 thickened, and somewhat crenulated. 



1. Columbella avara, Say. Shell fusiform, widest but little be- 



