[85] ALBATKOSS EXPLORATIONS. 587 



crowded, very fine, raised, longitudinal lines visible only under the 

 lens. Anterior aperture round with a sharp, thin edge ; posterior aper- 

 ture somewhat thickened, very small, round, slightly oblique, with a 

 deep, narrow, dorsal notch. Color delicate salmon, or yellow, gradually 

 shading into white toward the anterior end. Several dead specimens. 



Length, Sl.S'"'"; diameter of anterior aperture, 2™°i; posterior aper- 

 ture, about .S'n"*. 

 Cadulus Carolinensis Bush, sp. nov. 



B. range, 14 fathoms ;t 15 to 48 fathoms.* 



Shell of medium size, semi-transparent, very glossy, white, circular 

 throughout its entire length. Greatest diameter at about the anterior 

 third, diminishing slightly to the round, very oblique, anterior aper- 

 ture, and backward to the posterior end, at first very gradually and 

 farther back very rapidly. Curvature well marked in some specimens, 

 very slight in others, nearly uniform dorsally; but ventrally, most de- 

 cided in the posterior third. Posterior aperture very small, round, a 

 little oblique, with four small, distinct notches, two on each side. A 

 few living, and many dead specimens. 



Length, 9.5™°^ ; greatest diameter, about 2""'" ; diameter of anterior 

 aperture, l'""' ; posterior aperture, .4™°^. 



LAMELLIBRANCHIATA. 



jEnsatella Americana (Gould) Yerrill. 



B. range, 15 fathoms.t 

 Corbida disparilis D'Orbigny. 



B. range, 14 to 15 fathoms.t 

 Corbula Swiftiana C. B. Adams. 



B. range, 14 to 15 fathoms ; t 48 fathoms.* 

 Necera costata Bush, sp. nov. 



B. range, 48 fathoms.* 



I Shell moderately thick, compressed, triangular-ovate, with a contracted 

 and somewhat elongated rostrum, and with three or four very prominent, 

 curved, distant, radiating ribs on the convex part of the valves, and 

 with a few smaller and closer ones anteriorly. TJmbos high, smooth ; 

 beaks somewhat curved backward. The dorsal margin, from the beaks 

 to the end of the rostrum, is strongly and regularly concave, the ros- 

 trum being a little upturned or straight at the tip ; anteriorly, the 

 dorsal margin is convex, and falls off abruptly to the obtusely rounded 

 imterior end. The ventral margin is broadly rounded and projects out- 

 ward in an acute angle at the projection of each of the principal ribs; 

 the intervals between these angles are usually concave, and beyond the 

 hindermost rib the outline recedes in a concave curve to the origin of 

 the rostrum, which is rapidly narrowed to near the tip. Of the three 

 .principal radiating ribs, the middle one runs from the beak nearly to 



