414 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
anterior end short and roundly pointed; the posterior longer, obliquely pro- 
duced, rounded; resilium subumbonal, short, internal, left valve with two strong 
divaricating cardinal lamellae, one on each side of the resilium, rather short and 
prominent ; right valve with the margins so produced as to enclose the opposite 
pair; interior of valve polished, with a yellowish flush; margins entire and also 
the pallial lime. Longest dimension, 2.2; width at right angles, 1.7; diameter, 
1.4 mm. 
Dredged with the preceding species in Magellan Strait. U. S. N. Mus. 
110,714. 
A small but rather solid and characteristic little species. It is named in honor 
of the senior author of the Mollusks of Cape Horn. 
Rochefortia rochebrunei Datt, n. sp. 
Plate 17, figure 5. 
Shell small, subquadrate, compressed, white, inequilateral, with low, rather 
anterior beaks, and a pale yellowish periostracum ; anterior dorsal margin straight, 
sloping, anterior end rounded, basal margin nearly straight ; posterior dorsal mar- 
gin slightly convexly arcuate, near the end obliquely descending to a rounded 
point; outer surface somewhat irregularly concentrically striated ; interior pol- 
ished; resilium subumbonal, internal, with on each side of it a diverging lamella, 
stronger in the left valve. Length, about 4.5; height, 3.7; anterior end, 1.5 ; 
diam. 1.5 mm. 
Dredged in Magellan Straits with the two preceding species. U.S. N. Mus. 
110,718. 
This species is named in honor of the junior author of the Mollusks of Cape 
Horn. 
(CycLoponta) 
Cardiacea. 
Cardiidae. 
PROTOCARDIA Beyricu. 
This genus, of Mesozoic origin, is not sparsely represented in the recent fauna 
of the deep sea, and some of the most lovely of molluscan gems of the ocean 
are found among these species. But the extremely fragile spinose ornamenta- 
tion of the posterior area is almost always wanting, as a touch is enough to detach 
it even from the living shell. 
