408 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



eud of the liinge line, behind them a long, uarrow, 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 Hues, and three or four lines indicating resting 

 stages ; interior polished, white, the margins slightly notched by the external 

 sculpture but not internally creuulate ; 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. Ait. 35 ; lat. 32 ; diam. li ; hinge line, 11 ; posterior slope, 

 16 mm. 



U. S. S. "Albatross," station 3i04, 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 L. excavata, 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 Dall, n. sp. 



This little shell appears, on a casual glance, exactly like Limatula subauriculata 

 Montagu, but a careful comparison of specimens of tiie same size shows the 

 following differences : the hinge line is slightly shorter, the auricular angles less 

 prominent, and tiie 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 Z. subauriculata. Length of shell, 

 4.5; width, 2.7; diam. 2.0 mm. 



U. S. S. " 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 

 cruslied 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 Philippi. 



Lima pyymnen Philippi, Arch, fiir Naturg., \x\\, 1, p. 56. 



Hadtda (Limntnla) p,/tjmnea (ex fiarte) E. A. Smith. Pliil. Trans., 1870, 168, p. 191. 

 Zool. Kerguelen Id. (Moll., p. 25), pi. 10, fig. 16. 



