404 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.52. 



middle of the disk square reticulations with a small conspicuous 

 pustule at each intersection ; laterally these are more crowded ; right 

 valve concave near the margin, closely regularly concentrically 1am- 

 ellose; anterior ear with five radial lines, coarsely lameUose with a 

 shallow notch and serrate margin. Height, 14; breadth, 15; diam- 

 eter, 3 mm. Cat. No. 207273, U.S.N.M. 



Station 2986, southwest of San Diego, in 684 fathoms. 



The sculpture is sparser and partly obsolete near the beaks. 



PSEUDAMUSIUM BISTRIATUM, new species. 



Shell small, suborbicular, moderately convex, white, thin; left valve 

 finely concentrically, rather distantly lamellose, the lamellae closer 

 and more conspicuous on the subequal ears; radial scidpture of very 

 fine, close-set, uniform ahnost microscopic elevated fines, which do 

 not reticulate the lameUations; right valve with the concentric, but 

 without the radial sculpture, concave near the margin, the disk about 

 as convex as the other valve, ears subequal, byssal notch short, acute; 

 one or two fauit radii on the ear above it. Height, 7; breadth, 7; 

 diameter, 2 mm. Cat. No. 214056, U.S.N.M. 



Station 2923, off San Diego, California, in 822 fathoms. 



LIMATULA ATTENUATA, new species. 



Shell small, narrow, thin, white, radially sculptured with low, rather 

 close-set, rounded threads, crossed near the distal margin with low 

 concentric irregular lameUations so as to give that part of the valve a 

 minutely scabrous effect ; the medial radii are broader than the others 

 and radially striate, no mesial sulcus is noticeable but it is clearly indi- 

 cated on the inside of the valve; beaks low, incurved; area triangular, 

 resilif er large and excavated ; hinge margin short, strongly buttressed 

 on each side; valve margin crenulate. Height, 7; width, 3.6; diam- 

 eter, 4 mm. Cat. No. 220510, U.S.N.M. 



Nazan Bay, Atka Island, Aleutian chain. 



SEPTIFER BIFURCATUS, new variety, OBSOLETUS. 



Sliell large, the external sculpture obsolete, the distal part of the 

 valves nearly smooth. Cat. No. 173359, U.S.N.M. 

 San Diego Bay, mud flats. 



MODIOLUS (7POLITUS Verrill var.) PALLIDULUS, new species. 



Shell thin, smooth, brilliantly pofished, attenuated anteriorly, wide 

 and bluntly rounded behind, divided mto two color areas, the dorsal 

 large, translucent with a whitish zigzag reticulation, the ventral 

 opaque white with a yellowish tinge; hinge edentulous, margins 

 entu-e. Length, 23; maximum height, 11.5; beaks behind the 

 anterior end, 1; diameter, 5 mm. Cat. No. 212746, U.S.N.M. 



