872 I'ROCEEDINGS OF THE NATIONAL MUSEUM. VOL.XX. 



the teeth. In the left valve, there are eleven anterior and nine pos- 

 terior teeth. The surface of the shell is dull yellowish green, only 

 slightly iridescent, and covered with irregular lines of growth which, in 

 some places, form irregular raised lines. The umbos are but little 

 prominent; the beaks are small and turn backward. 



Length, 3.G mm.; height, 2.5 mm. 



One specimen (No. 78363), station 2097, N. lat. 47 40', W. long. 47 

 35' 30", in 206 fathoms, 1886. 



This species is peculiar in its nearly equilateral, elliptical form, with 

 the dorsal margins gently convex and only slightly sloping both sides of 

 the beaks, and especially in its large resilial notch which cuts entirely 

 through the hinge-plate. It agrees pretty closely with Jeffreys 7 type, 

 but the latter was much smaller and his figures and diagnosis are too 

 imperfect to make its identity certain. 



YOLD1ELLA FRIGIDA (Torell). 



(Plate LXXIX, fig. 4.) 



Toldia friffida VERRILL, Trans. Conn. Acad., V, p. 573, pi. XLIV, fig. 2, 1882; VI, 

 p. 279, 1884 (in part) ; Expl. Albatross, Eeport U. S. Coin. Fish ami Fisheries 

 for 1883, p. 576, 1885 (in part). 



A very few specimens, at about ten stations, between N. lat. 43 5', 

 W. long. 70 11' 30", and N. lat. 39 53' 30", W. long. 71 13' 30", in 88 

 to 312 fathoms, 1874-1881. 



YOLDIELLA DISSIMILIS, new species. 

 (Plates LXXVIII, fig. 8; LXXX1I, fig. 7.) 



Toldia exfxinsa VERRILL, Trans. Conn. Acad., VI, p. 279, 1884 ; Expl. Albatross, Ee- 

 port U. S. Corn. Fish and Fisheries for 1883, p. 576, 1885 (not of Jeffreys). 



Shell small, oblong-ovate, nearly equilateral, with the anterior end 

 the broader and bluntly rounded, the posterior end somewhat narrowed 

 medially and bluntly rounded, without any distinct augulation. Umbos 

 somewhat prominent; beaks small and strongly incurved. Surface 

 straw-colored, not lustrous, covered with fine concentric lines. Antero- 

 dorsal margin but little curved, sloping very gradually to the anterior 

 end which is curved nearly in the arc of a circle; ventral margin very 

 broadly rounded with a very slight obtuse augulation behind the mid- 

 dle; postero-dorsal margin slightly excavated just behind the beaks, 

 then sloping very gradually to the obtuse posterior end. The hinge- 

 margin is moderately stout; the two portions form a very wide angle 

 at the beak with the anterior, which faces obliquely downward, consid- 

 erably the more arched. In the center the margin becomes very thin 

 and is interrupted by the resilium which occupies a deep notch and an 

 internal shelf of considerable size, situated far back and directed down- 

 ward to such an extent that it is only partially visible in a direct front 

 view ; there are about eleven or twelve anterior, and eight to ten poste- 



