408 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
end of the hinge line, behind them a long, narrow, faintly radially striated, exca- 
vated escutcheon; anterior slope very short, straight; posterior long, oblique, 
slightly excavated; remainder of the valve margins evenly, ovately arcuate ; disk 
sculptured with about fifty flat, polished, radial ribs with narrow, channelled 
interspaces, each about one third the width of the intervening ribs; concentric 
sculpture only of faint, incremental lines, and three or four lines indicating resting 
stages; interior polished, white, the margins slightly notched by the external 
sculpture but not internally crenulate; muscular scars rounded, faint, rather 
small; hinge with a single obsolete tubercle in each valve at each end; the 
valves do not gape perceptibly, except a narrow chink in the middle of the 
escutcheon. Alt. 35; lat. 32; diam. 14; hinge line, 11; posterior slope, 
16 mm. 
U. S. S. “Albatross,” station 3404, near the Galapagos Islands, in 385 
fathoms, rocky bottom, temperature 43°.2 F. U.S. N. Mus. 122,875. 
Although a small shell when compared with such giants as LZ. ercavata, the 
characteristics are such as to place it in the same section of the genus. It differs 
from the young of either of the large species, so far as known, by its short and 
broad shape, thick and heavy shell, and strong, radial sculpture. 
Lima (Limatula) similaris Datt, n. sp. 
This little shell appears, on a casual glance, exactly like Limatula subauriculata 
Montagu, but a careful comparison of specimens of the same size shows the 
following differences: the hinge line is slightly shorter, the auricular angles less 
prominent, and the area between the beaks less wide, the socket for the ligament 
consequently is shorter and more feeble; the surface is covered with radial 
threads which cover most of the disk instead of being strong only near the ventral 
margin; there is no radiating medial sulcus, so prominent in L. subauriculata, 
either within or without the shell, and the slight obliquity or lateral deviation of 
the ribs is in the opposite direction from that in LZ. subauriculata. Length of shell, 
4.53; width, 2.7; diam. 2.0 mm. 
U. S. 8. “Albatross,” station 2799, in 30 fathoms, mud, Panama Bay. 
U.S. N. Mus.. 109,034. 
Only one valve of this little shell was obtained, and that was unfortunately 
_erushed by accident after the above diagnosis had been prepared. A second 
specimen, somewhat smaller, was obtained at 2983, in fifty-eight fathoms, sand, 
off Cerros Island, Lower California, bottom temperature 55° F. In this a slight 
trace of a mesial furrow between two small threads appears on the inside of the 
shell, but none on the external surface. 
Lima (Limatula) pygmaea Puiirrt. 
Lima pygmaea Philippi, Arch. fiir Naturg., 1841, 1, p. 56. 
Radula (Limatula) pygmaea (ex parte) E. A. Smith, Phil. Trans., 1870, 168, p. 191. 
Zool. Kerguelen Id. (Moll., p. 25), pl. 10, fig. 16. 
