NO. 1139. DEEP-WATER MOLLUSC A VERR1LL AND HI '.s 1 //. 791 



CRYPTODON (AXINULUS) INEQUALIS, new species. 

 (Plate KC, li-s. 1, 2.) 



Shell small, somewhat oblong, with the anterior end much the longer. 

 Umbos rather prominent, beaks elevated, curved strongly forward, so 

 as to leave a small, deep limular area. The antero-dorsal margin is at 

 first nearly straight, sloping but little, and is nearly parallel with the 

 ventral margin; the anterior end is produced, broadly and evenly 

 rounded ; the ventral margin is much less rounded, with the middle 

 portion almost straight for a short distance, toward the posterior end 

 it is subtruncate and slightly angulated; the postero-dorsal margin is 

 convex and slopes rapidly; a very slight depression runs from the 

 beak to the postero- ventral margin, but is so slight as to be scarcely 

 worthy the name of plication or fold; posterior to this there is a dis- 

 tinct submargiual ridge separated by a rather deep groove, from the 

 ligameutal area, which is long and narrow. The surface appears to 

 the naked eye nearly smooth, bluish white; under the microscope it is 

 marked by slight, raised, concentric ridges and faint undulations, 

 which are the most regular and distinct on the urabos. In addition to 

 these the whole surface, when highly magnified, has a fine fibrous 

 appearance; on some parts there are remnants of a thin, pale yellow- 

 ish epidermis. The hinge-margin is distinctly thickened, with a slight 

 protuberance directly under the beak, where it is thicker than else- 

 where. The posterior ligament is rather large and strong, and occu- 

 pies a conspicuous groove extending from under the beak about one- 

 third the length of the postero-dorsal margin. 



Length, 4.5 mm.; height, 4.25 mm.; thickness, about 4 mm. 



A few specimens have been found in 14 to 49 fathoms, at about eleven 

 stations north of Cape Cod, in Casco Bay, and in Halifax Harbor, 

 1873-1879. 



CRYPTODON (AXINULUS) SIMPLEX, new species. 

 (Plate XCII, figs. 3, 4.) 



Shell small, thin, fragile, translucent bluish white, somewhat inflated, 

 nearly circular in outline and without any posterior undulations. Beaks 

 small, acute, slightly prominent, turned forward. Antero-dorsal mar- 

 gin excavated in front of the beaks and convex farther forward; ante- 

 rior margin broadly and evenly rounded and, with the ventral margin, 

 forms nearly a circular curve; the posterior margin similarly rounded, 

 but slightly flattened in the middle j postero-dorsal margin broadly 

 convex without any distinct angulation posteriorly. The surface is 

 nearly smooth and somewhat glossy on the umbos; it is marked by 

 rather indistinct, small, concentric waves or undulations and micro- 

 scopic lines of growth. Interior somewhat shining. The hinge-margin 

 is thin, delicate, and very simple, with but a very slight thickening in 

 the region of the beak; a narrow groove for the ligament is visible just 



