14 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Type in Museum Cuming, London. Type locality, Dunbar, Britain. 
Range. Point Barrow, Alaska, to Coronado Islands, California. Cir- 
cumboreal. In the Pliocene at San Pedro, and San Diego, California. 
Nucula tenuis expansa Reeve, 1855. 
Plate 13, figs. 6, 7. 
Last of the Arctic Voy., App., p. 397; tablet 33, fig. 2. 
Shell large, ovate-triangular, tumid, the surface distinctly nucleated 
with ridges, both dorsal areas with fine radiating striae; ten teeth in front 
and fifteen behind the beaks. Dark chestnut colored. (Reeve.) 
Type in Mus. Belcher Cabinet. Type locality, Northumberland Sound, 
Arctic Ocean. 
Range. Arctic Ocean to Sitka, Alaska, and San Diego, California. 
Nucula darella Dali, 1916. 
Proc. U. S. N. M., 52:394. 
Shell small, inflated, subtriangular, the anterior end slightly shorter; 
periostracum dark olive, the surface smooth except for somewhat irregu¬ 
lar, inconspicuous incremental lines, but under a lens showing faint close 
radial striae; lunule large, distinctly limited by an impressed line, mesially 
with a slight pout; about five anterior and eight posterior hinge teeth, the 
resilifer deep, small, central, not projecting; inner margins of the valves 
sharply radially grooved; beaks pointed, showing the prodissoconch 
plainly. Length, 4; height, 3; diameter, 2.7 mm. (Dali.) 
Type in U. S. N. M., No. 111424. Type locality, Station 2923, off 
San Diego, California, in 822 fathoms. 
Range. Known only from the type locality. 
Subgenus Acila H. & A. Adams, 1853. 
Nucula castrensis Hinds, 1843. 
Plate 5, fig. 11, and plate 37, figs. 1, 2. 
Proc. Zool. Soc., 1843, p. 98, Conch . Iconica, 18; pi. 4, species 32. 
Nuc. testa elliptica, antice rotundata, epidermide olivaceous induta; 
lineis divaricatis; marginibus ventralibus crcnulatis; cardine antice denti- 
bus 5, postice 11. Long. 3; lat., iy 2 ; alt., .2 lin. (Hinds.) 
Shell small, elevated, subtrigonal, sculptured with raised lines diverg¬ 
ing from the centre, pale straw banded with reddish brown; posterior 
side sloped, anterior side rather convex. 
Type in Cabinet Belcher. Type locality, Sitka, Alaska. 
Range. Bering Sea to San Diego, California. In the Pleistocene at 
Santa Barbara, San Pedro and San Diego; the Pliocene at San Fernando, 
San Pedro, San Diego; and the Miocene in Oregon and Washington. 
