DALL: MOLLUSCA AND BRACHIOPODA. 369 
into the convex arcuation of the basal margin; surface polished on the umbones, 
on the disk and periphery more or less minutely, irregularly wrinkled, especially 
near the truncation and the basal margin ; there are also a few very faint, almost 
microscopic, irregularly distributed radial striae; interior of the valves slightly 
pearly, the muscular and pallial scars faint, the latter entire ; margin of the valves 
simple, smooth; hinge with six cardinal teeth on the shorter and ten on the 
longer side; chondrophore small, narrow, directed obliquely forward; lon. of 
valve, 17; of the beaks before the truncation, 7; alt. 11; diam. 6.5 mm. 
U. 8. 8. “ Albatross,” station 3417, off Acapulco, Mexico, in 493 fathoms, 
mud, bottom temperature 40°.6 F. U.S. N. Mus. 122,897. 
There is more or less difference between individuals in regard to rostration, 
some having it more emphatic than others. In form this species somewhat 
approaches Leda, but there is not the slightest pallial sinuation. 
Nucula iphigenia Dat. 
Plate 7, figures, 1, 4. 
Nucula iphigenia Dall, Proc. U. S. Nat. Mus., 1895, 18, p. 15. 
Shell large, solid, much like Iphigenia brasiliana in outline, anterior end pro- 
duced, rounded, longer than the posterior; hinder end obliquely truncate, atten- 
uated; beaks elevated, somewhat pointed, opisthogyrous; sculpture of feeble, 
narrow, irregular concentric wrinkles, crossed by fine, sharp, rather distant 
incised lines; lunule narrow, elongate, bordered by a faint ridge; escutcheon 
small, broader than long, set off by an impressed line from the large posterior 
area, which is flattened but not definitely limited, the margin of the valve project- 
ing somewhat in the middle line; base rounded in front, somewhat impressed 
posteriorly ; interior brilliantly nacreous, with a strong pallial line and subequal 
adductor scars; the pallial area more or less punctate; basal margin denticulate ; 
hinge with about thirty anterior and fifteen posterior teeth, strong, projecting, 
and somewhat angular; chondrophore narrow, pear-shaped, projecting forward 
from the hinge line. Height of shell, 22.5; length, 35; diameter, 16 mm. 
U.S. S. “ Albatross,” station 3396, Gulf of Panama, in 259 fathoms, hard 
bottom; temperature, 47°.4 F. U.S. N. Mus. 122,895. 
This fine shell is one of the largest known nuculas, and peculiar from its elongated 
shape and posterior attenuation. The periostracum seems to have been thin, 
dull, and yellowish. 
Nucula pigafettae Da t, n. sp. 
Shell small, blackish-brown or dark olivaceous, rude, inequilateral, concentri- 
cally irregularly striated, the striae more or less distributed in zones, very minutely, 
feebly, more or less radially striated, but not visibly reticulate; beaks rather pos- 
terior, turgid, moderately prominent; a heart-shaped escutcheon 5 mm. long 
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