387 



they become nearly obsolete ; straight, entire, not furcate ; long 

 and short ribs alternating. Back broad, anterior and posterior 

 third convex ; middle third concave, anterior third, studded with 

 small tubercles. Tubercles on anterior and posterior thirds of 

 carinas small, nearly obsolete: on the middle third of each carina, 

 seven very large tubercles, broad at the base ; compressed laterally 

 near the apex ; terminating in an acute edge, curving outwardly. 

 Sinus furnished with a thick callus continued to the margin of 

 the lip. Lips convex. Aperture subquadrate oblong ; narrowing 

 somewhat anteriorly. Angles acute ; spineless ; everted. An- 

 terior half of the shell milk white, except near the sinus, where 

 it is pale purple ; posterior half pale fuscous. Subsinus, carinag, 

 and large tubercles, dark fuscous ; a white, longitudinal, central 

 line running through it, between carinas. Anterior half of shell 

 polished, remainder dull. 



Length, 2|- inches. Breadth, 1^ inches. Aperture : length, 

 1^ inches ; width, 1 inch. Obtained at New Nantucket, Pacific 

 Ocean. 



I have named this shell after the distinguished T. A. Conrad, 

 whose labors in the Testaceological field are well known and 

 universally appreciated. 



No. 2. A. Fragilis. — Oblong ovate, very thin, frail, sides 

 smooth, without granulations, having numerous opaque, minute 

 milk-white spots distributed over them ; ribs numerous, inter- 

 rupted, a few entire ; subfurcate, somewhat waved. Back narrow, 

 flat. Tubercles many ; rather small ; generally of a size. Sinus 

 large, furnished with a callus, which is attenuated towards the 

 edge of the lip, and is carried across the base of the aperture, 

 from one sinus to the opposite, in a flattened arch ; upon this 

 arch rests one side of the nucleus of the shell ; which is not in- 

 voluted like other species, but rises in a cylindrical form, a half 

 inch above the arch from which the inner side springs ; it has 

 much the appearance, in shape, of the end of the finger of a 

 glove. Around this cylinder are a number of lines of growth ; 

 otherwise it is smooth, somewhat waved, and destitute of tuber- 

 cles for the distance of ^ inch from the apex ; lips convex. 

 Aperture, ovate oblong. 



Color white, except the apex and posterior half of nucleus 



