406 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
irregular, often eroded; left valve with small subequal, minutely concentrically 
lamellose ears; posterior submargin smooth or only with incremental lines; disk 
with fine incremental lines crossed by numerous fine radial lines with wider inter- 
spaces, increasing by intercalation ; these radii are arcuate, slightly convex on the 
anterior side, and bending gently toward the posterior; the radii are not scaly; _ 
right valve flexible toward the ventral margin, the portion beyond the internal 
lirae slightly reflexed when the valves are closed ; ears similar and similarly sculp- 
tured, the anterior with no byssal sulcus, though there is a single feeble ray near 
the submargin and a slight inward flexuosity of the incremental lines; disk regu- 
larly concentrically striated, the striae with wider interspaces, the intact surface 
covered with a thin, dehiscent, coarsely fibrous layer; interior polished, the cen- 
tral part whiter, with nine regular, even white, elevated lirae extending all the way 
from the umbonal region without noticeable thickening distally ; in each valve are 
also two short auricular crura. Height of shell, 18.2; breadth, 18.5 ; hinge line, 
8.2; diam. 3.4 mm. 
U.S. S. “ Albatross,” station 3360, Gulf of Panama, in 1672 fathoms, sand, 
bottom temperature 42° F. U.S. N. Mus. 122,871. Also abundantly, near 
Malpelo Island, at station 3374, in 1823 fathoms, ooze, temperature 36°.4; 3381, 
in 1772 fathoms, mud, temperature 35°.8; 3361, in 1471 fathoms, ooze, tempera- 
ure 36°.6; and 3684, in Mid Pacific, latitude 0° 50’ N., longitude 137° 54’ W.., 
in 2463 fathoms, ooze, temperature about 35° F. 
This is an abundant but not particularly attractive abyssal species, sufficiently 
distinct from any of the Atlantic species. 
Spondylidae. 
PLICATULA Lamarck. 
Plicatula dubia Sowersy. 
Plicatula dubia Sowerby, Thes. Conch., 1847,1, p. 436, pl. 91 (only), fig. 19. 
U.S. S. “ Albatross,” station 2798, in Panama Bay, in 18 fathoms; U. S. N. 
Mus. 96,262. Cana Island, West Columbia, Cuming. 
Limidae. 
LEWEA CovieEr. 
Lima s.s. 
Lima 8.8. Dall, Trans. Wagner Inst., 1898, 3, p. 765; type ostrea lima Linné. 
MANTELLUM Apams. 
Lima (Mantellum) hians GME Lin. 
Ostrea hians Gmelin, Syst. Nat., 1791, 1, pt. 6, p. 8832, no. 97. 
Lima hians Hanley, Rec. Shells, 1848, p. 268, footnote. 
