380 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
ORTHOYOLDIA Verritt anp Busa. 
Orthoyoldia Verrill and Bush, Amer. Journ. Sci., 1897, ser. 4, 3, p. 55; type, Yoldia 
scapania Dall. 
Yoldia (Orthoyoldia) panamensis Da tt, n. sp. 
Shell small, narrow, elongate, very inequilateral, brilliantly polished, glassy with 
an olivaceous periostracum, rather compressed but not flattened; beaks very low, 
inconspicuous, adjacent ; lunule and escutcheon almost linear, bounded by low 
but distinct ridges; surface absolutely smooth except for faint traces of incre- 
mental lines; dorsal slopes almost straight, the anterior much shorter; extremi- 
ties subequally rounded, the posterior somewhat the most blunt; base a little more 
convex in front of and under the umbones; profile slightly attenuated behind the 
umbones; interior glassy, scars invisible, hinge plate with eighteen interior and 
52-97 posterior, small, subequal teeth ; margins entire. Lon. of shell, 16.5; of 
beaks behind anterior end, 6.5; alt., 7.5; diam., 4.0 mm. 
U. S. S. “ Albatross,” station 3354, Gulf of Panama, in 322 fathoms, mud, 
bottom temperature 46° F. U.S. N. Mus. 122,900. Also at station 33855, in 
182 fathoms, shelly bottom, temperature 54°.1 F. 
The resilium is small, vertical, triangular, and wholly internal. There is no 
visible external ligament. 
This species groups with the Y. scapania Dall, from the South Atlantic and 
Y. solenoides Dall, from the West Indies. 
YOLDIELLA Verritt anp Bus. 
Yoldiella Verrill and Bush, Amer. Journ. Sci., 1897, ser. 4, 3, p. 55; type, Yoldia 
lucida Lovén. 
Yoldia (Yoldiella) chilenica Dax1, n. sp. 
Shell small, tumid, white with a polished pale yellow periostracum, inequilateral, 
the anterior side shorter, rounded; posterior longer, rounded below, straight 
above, and almost pointed at the upper posterior angle; ligament obscure, amphi- 
detic; beaks low, adjacent, showing the protoconch ; no lunule, a feebly impressed 
escutcheon with the valve margins medially prominent ; surface of the disk feebly, 
irregularly, concentrically striated; valves not gaping; interior white, porcel- 
lanous, with a wide but short pallial sinus, rounded in front; seventeen posterior 
and nineteen anterior hinge teeth separated by a short gap with a small, deep, 
triangular pit for the resilium. Length of shell, 11.5; of posterior end, 6.0; alt. 
6.5; max. diam. 5.2 mm. 
U.S. S. “ Albatross,” station 2781, on the southern coast of Chile (Lat. 51° 
