DALL: MOLLUSCA AND BRACHIOPODA. 441 
about 250 fathoms, of which two specimens were obtained, is a distinct species, 
Which so far as we know does not reach the Magellanic region. 
TELOTREMATA. 
Rhynchonellacea. 
Rhynchonellidae. 
HEMITHYRIS D'ORBIGNY. 
Hemithyris craneana Datu. 
Henithyris craneana Dall, Proc. U. S. Nat. Mus., 1894, 17, p. 717, pl. 31, figs. 5, 6. 
U.S.8,« Albatross,” station 3362, off Cocos Island, Gulf of Panama, in 1175 
fathoms, mud, bottom temperature 369.8 F. U.S. N. Mus. 122,861. 
A species of the general type of H. cornea Fischer, of the North Atlantic. 
Only one specimen was obtained. 
Hemithyris strebeli Daz, n. sp. 
Shell extremely thin and fragile, of a translucent very pale gray color, markedly 
Wider than high, smooth and polished, except for occasional concentric lines due 
O resting stages; the surface under a lens shows a coarse prismatic structure, 
the imbrieating ends of the prisms almost giving the effect of fine punctation ; 
eak low, sharp, small, with a wide delthyrium, widely triangular diserete del- 
tidia] plates, and a small foramen, incomplete below; dorsal valve in the young 
flattish, in the adult deeply widely excavated mesially, with the anterior margin 
Prominently extended into a correspondingly wide sinus in the margin of the 
ventral valve; ventral valve convex, in the adult almost trilobed with a broad, 
Prominent mesial anterior convexity and corresponding marginal sulcus; interior 
a dorsal valve with a short, very low, thread-like septum about equal to one 
IN the height of the valve; the hinge teeth close together, small, short, with- 
= pe muscular impressions obscure; crura short, blade-like, recurved, very 
Suly detached ; ventral valve with no septum, the hinge teeth propped by plates 
EM which and the valve are narrow recesses, Alt. 17 ; lat. 19; lat. of median 
Us, 11; max. diam. 9.5 mm. 
ag 8. 8, « Albatross,” station 4721, in Mid Pacific, in 2084 fathoms, globiger- 
4709 oze, bottom temperature 359.1 F. U. S. N. Mus. 110,741. Also at station 
Pi ow of the Galapagos group, in 2035 fathoms, ooze, temperature 
a Shell is distinguishable from any other described species by its low beak, 
e trilobate form, and especially by having the median suleus concave in the 
