NO. 1139. DEEP-WATER MOLLUSCAVERRILL AND BUSH. 865 



just beneath the beak, forms a notch which completely interrupts the 

 hinge-margin. 



Length of one of the largest specimens, 6 mm.; height, 4.5 mm., 

 thickness, 3 mm.; from beak to posterior angle, 4 mm. 



Found in considerable numbers, at about twenty stations, between IT. 

 lat. 41 53', W. long. 65 35', and K lat. 35 <)' 50", W. long. 74 57' 40", 

 in 516 to 1,608 fathoms, 1883-1886. Several live specimens, at station 

 2079, in 75 fathoms. 



This species is closely related to 1". htcida, (Loven), from whicli it is 

 easily separated by its shorter, broader, more swollen form, its strongly 

 curved ventral margin, and very distinct postero-dorsal angle. It is 

 shorter and bas a broader posterior end than most of the related 

 species. The resilium is not visible externally. 



YOLDIELLA SUBANGULATA, new species. 

 (Plates LXXVII, fig. 3; LXXIX, fig. 6.) 



Very similar to the preceding species in form but less pointed pos- 

 teriorly and larger. The umbos are small, not prominent; beaks are 

 small, directly incurved, appressed to the hinge-margin but not dis- 

 tinctly notched by the resilial pit. The antero-dorsal margin is convex, 

 arched; the anterior end is a little produced, obtusely rounded; ven- 

 tral margin evenly and broadly rounded, slightly produced posteriorly, 

 forming an obscure obtuse angle as it merges into the posterior end 

 which is obliquely subtruncated or a little iuflexed in the middle, with 

 a prominent dorsal angle; the postero-dorsal margin slopes but little, 

 and is nearly straight, with the compressed edges forming a slight keel, 

 which is a little convex in the middle. A well-marked ridge runs to 

 the postero-dorsal angle, and a less distinct one to the postero-ventral 

 angle; between these there is a slight depression of the surface. Sur- 

 face nearly smooth, lustrous, reflecting prismatic colors, and covered 

 with faint lines of growth and a few inconspicuous irregular stilci; 

 epidermis pale olive yellow. The hinge-margin is narrow, very obtusely 

 angled, and is interrupted under the beaks by the small notch-like 

 resilial pit. The anterior series of teeth is slightly arched and con- 

 tains about seventeen teeth, including three or four minute proximal 

 ones; the larger ones are high and sharp. The posterior series is a 

 little longer and contains about eighteen, similar, but somewhat more 

 slender teeth. A thin, smooth margin extends along outside both series. 

 There is a small internal denticle at the front edge of the resilial pit. 

 Pallial sinus narrow, considerably inflexed. 



Length, 8 mm. ; height, 5 mm. ; thickness, about 4 mm. ; from beak to 

 anterior end, 3 mm.; posterior end, 5 mm. 



One live specimen was dredged by the Baclie at station 46, 1ST. lat. 

 43 3' ; W. long. 70 4', in 51 fathoms, 1874. 



Proc. N. M. vol. xx 55 



