380 bulletin: museum of comparative zoology. 



ORTHOYOLDIA Verrill and Bush. 



Orthoyoldia Verrill and Bush, Amer. Journ. Sci., 1897, ser. 4, 3, p. 55; type, Yoldia 

 scapania Dall. 



Yoldia (Orthoyoldia) panamensis Dall, n. ep. 



Shell small, narrow, elongate, very inequilateral, brilliantly polished, glassy with 

 an olivaceous periostracum, ratlier 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 

 umboues; interior glassy, scars invisible, hinge plate with eighteen interior and 

 52-27 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. TJ. S. N. Mus. 122,900. Also at station 3355, 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 T. scapania Dall, from the South Atlautic and 

 Y. solenoides Dall, from the West Indies. 



YOLDIELLA Verrill and Bdsh. 



Yoldiella Verrill -and Busli, Amer. .lourn. Sci , 1897, ser. 4, 3, p. 55 ; type, Yoldia 

 lucida Loven. 



Yoldia (Yoldiella) chilenica Dall, 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 tiie 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° 



