406 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



irregular, ofteu 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 sliglit 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 umboual region without noticeable thickening distally ; in each valve are 

 also two short auricular crura. Height of shell, IS. 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° P. 



This is an abundant but not particularly attractive abyssal species, sufficiently 

 distinct from any of the Atlantic species. 



Spondylidae. 



PLICATULA Lamarck. 



Plicatula dubia Sowerbt. 



Plicatula dubia Sowerby, Thes. Conch., 1847,1, p 436, pi. 91 (only), flg. 19. 



U. S. S. " Albatross," station 2798, in Panama Bay, in 18 fathoms ; U. S. N 

 Mas. 96,262. Cana Island, West Columbia, Cuming. 



Limidae. 



LIITIA CcviER. 



Lilma s. s. 



Lima 8. 9. Dall, TranB. Wagner Inst., 1898, 3, p. 765; type oitrea lima Linn^. 



MANTELLUM Adams. 

 Lima (Mantellum) hians Gmelin. 



Ostrfa h{an$ Gmolin, Syst. Nat., 1701, 1, pt. 0, p 3332, no. 97. 

 Lima hians Hanley, Rt'C Shells, 1843, p. 268, footnote. 



