DALL: MOLLUSCA AND BRACHIOPODA. 371 
Conspicuously as two whitish disks on the umbones, smooth and easily eroded ; 
beaks subcentral, touching, not recurved; lunule and escutcheon large for the 
size of the shell, with no radial markings and faintly delimited but not distinctly 
impressed ; ligament not visible externally ; posterior dorsal slope straight, poste- 
rior end shorter and somewhat pointed ; anterior slope slightly convexly arcuate, 
anterior end rounded ; base very convexly arcuate; concentric sculpture only of a 
few irregularly distributed impressed lines indicating resting stages; radial seulp- 
ture of numerous very fine, slightly raised, close-set lines, with equal and regu- 
larly spaced interspaces, covering the disk; interior pearly, smooth, with entire 
valve margins, muscular scars distinct; hinge line with six posterior and ten 
anterior teeth, the two series separated by a deep pit containing the nearly 
vertical chondrophore. Lon. 5.0; alt. 4.5; diam. 3.0 mm. 
U. $, S. * Albatross,” station 4656, off the coast of Peru in S. Lat. 6°55’ and 
W. Lon. 83° 34/, in 2222 fathoms, green mud, bottom temperature 35% F. 
U. 8. N, Mus. 110,572; station 2792, off Manta, Ecuador, in 401 fathoms, mud, 
temperature 499.9 ; and station 3418, off Acapulco, Mexico, in 660 fathoms, sand, 
temperature 39°, 
à This is an exceedingly elegant little shell with a wide range in latitude and 
epth, 
Nucula declivis Hinos. 
Nucula declivis Hinds, P. Z. S. London, 1843, p.97; Zool. Voy. Sulph., 1844, 
Moll., p. 63, pl. 18, fig. 8. 
UNS « Albatross," station 9805, Panama Bay, in 51 fathoms, mud. Also at 
Station 2778, in Magellan Straits, in 61 fathoms, sand, bottom temperature 
175.9 F, U.S., N. Mus. 110,685. 
The locality of this species is not, given by Hinds, but his excellent figure and 
brief description agree well with the shell above referred to, and as his collections 
Were largely made on the Pacific coast of south and middle America it is probable 
that the identification is correct, 
Nucula colombiana Darr, n. sp. 
Shell small, very inequilateral, ovate, white with an olivaceous pale periostra- 
Cum, smooth, brilliantly polished, anterior dorsal margin and base convexly 
arcuate; posterior dorsal margin short, straight, subtruncate, with the valve- 
margins pouting a little in the middle of the flattened posterior area; posterior 
end attenuated, short, almost pointed; anterior end evenly rounded; beaks 
turgid, Opisthogyrate; interior pearly, with smooth margins to the valves; 
Posterior hinge line with seven, anterior with fourteen teeth, separated by a well- 
developed chondrophore. Length of whole shell, 4.5; of posterior segment, 1.0; 
alt, 3.0; max. diam. 2.2 mm. 
