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, tlie 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 ; Ion. of 

 valve, 17; of the beaks before the truncation, 7; alt. 11 ; diam. 6.5 mm. 



U. S. S. "Albatross," station 3417, off Acapuico, Mexico, in 493 fathoms, 

 mud, bottom temperature '10°.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 sinuatiou. 



Nucula iphigenia Dall. 



Plate 7, flgures, 1, 4. 

 Nucula iphigenia Dall, Proc. U. S. Nat. Mus., 1895, 18, p. 15. 



Shell large, solid, much like Tp/iit/enia 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 paUial 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°.-i 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 Dai.l, 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 



VOL. XLIII. NO. 6 24 



