876 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL.XX. 



near the ventral margin these become more elevated, clearly defined, 

 and are separated by wider, slightly concave grooves. The hinge-plate 

 is rather thin and delicate, regularly curved, without any angle at the 

 beaks, with the posterior portion considerably the longer. There is a 

 small, median, specialized ligament which occupies a lunate, or nearly 

 semicircular notch in the hinge-plate directly beneath the beak, which 

 does not extend through its entire width although it is here quite nar- 

 row. The posterior ligament is pretty well developed and extends 

 from the beak, where it is closely connected with the median portion, 

 nearly to the distal end of the series of teetb, and occupies a distinct 

 marginal groove; the portion nearest the beaks, opposite the smaller 

 teeth, is thicker and darker colored than the rest and projects slightly, 

 in a dorsal view; a delicate, inconspicuous portion continues a little in 

 front of the beak, in a thin groove. The median portion of the liga- 

 ment is so closely connected with the posterior portion that it appears 

 to be a specialized, thickened portion of it, but is evidently homologous 

 with the resilium of other genera; it is situated, however, outside the 

 series of teeth and must serve as a ligament. Tlie larger teeth are deli- 

 cate, subacute, V shape, compressed in a direction parallel with the 

 dorsal margin, with deep pits between them. There are about ten in 

 the anterior series, including three or four, very small, scarcely raised 

 ones next the beak; and fourteen in the posterior series, of which the 

 seven distal ones are decidedly larger than the rest, the tenth to the 

 thirteenth being the largest; about four, next the proximal end of the 

 series, are like small, rounded tubercles or granules without a V-shape 

 form; following these are three of intermediate form, increasing in size 

 distally, the seventh being more or less V-shaped; these smaller teeth 

 form a series along the inner edge of the hinge-plate. An edentulous 

 ridge, about as long as the space occupied by the first three teetb, 

 extends from the first tooth to the ligament-pit and is continuous with 

 a similar, thinner ridge running below the ligament-pit to the anterior 

 series of teeth. The pallial sinus is of moderate size and triangular iu 

 form. 



Length, 5 mm.; height, 4 mm. 



One live specimen (No. 52159), station 2566, off Chesapeake Bay, in 

 2,620 fathoms, 1885. 



MALLETIA POLITA, new species. 

 (Plate LXXXII, fig. 10.) 



Shell of moderate size, irregularly ovate, somewhat swollen, the ven- 

 tral region convex and the posterior end somewhat produced with a 

 short rostrum. Epidermis light yellow, lustrous and iridescent, limbos 

 not prominent, beaks small, strongly incurved, only slightly elevated 

 above the margin. The antero-dorsal margin is slightly convex and 

 slopes gently to the short, obtusely rounded anterior end which is 

 slightly augulated in the middle; the ventral margin is strongly con- 



