318 AXEL A. OLSSON 



Family COOPEKELLIDAE 



A group of small shells, usually with thin, veneriform valves, the 

 surface white and glossy, sometimes weakly undulate or marked with 

 fine lines of growth only. Hinge as described for the genus. 



Genus COOPERELLA Carpenter, 1864 

 {Oedalia Carpenter, 1864, not of Meigen, 1820 (Diptera). Oedalina 

 Carpenter, new name for Oedalia). 



Type species by monotypy, Oedalia (Cooperalla) scintillaeformis Car- 

 penter {z=Oedalia subdiaphana Carpenter). 



Shell small, thin and fragile, white, ovately subtriangular, equivalve, 

 the umbones submedian, convex, the surface smooth or concentrically 

 striated or undulated. Hinge plate narrow, bearing the cardinal teeth, in 

 the forward section ^nd a short, oblique, and partly immersed resilifer in 

 fhe back, and separated from each other by a thin olafe. The cardinal set 

 has three teeth in the left val /e and two teeth in the right valve, placed 

 directly under the beaks; the central cardinal tooth is always bifid, the 

 others sometimes so; there arc no lateral teeth. Adductor scars are small, 

 ovate, connected by the pallial sinus bearing an ample sinus. The inner 

 margins of the valves are smooth. 



Cooperella subdiaphana (Carpenter) Plate 84, figure 4 



Oedalia subdiaphana Carpenter, 1864, Kept. Brit. Assoc. Adv. Sci. for 1863, p. 639, 



n.g., n.s. Thin, swollen, shape of Kellia, ligament surrounding beaks; hinge 



with 5 bifid teeth (3-2); no laterals; large mantle bend. Reprinted in Smith. 



Misc. Coll. no. 25q, A, p. 125, No. 56. — Carpenter, 1865, Jour, de Conchy., vol. 



13, p. 134, reprinted Smith. M. p. 302. 

 Cooperella scintillaeformis Carpenter, 1864, op. cit., p. 639, No. 57. New subgenus of 



Oedalia. Cartilage semi-internal; only 1 tooth bifid. Reprinted, Smith, op. cit., 



p. 125. 

 Oedalina subdiaphana (Carpenter), 1865, Proc. California Acad. Nat. Sci., vol. 3, p. 



208. — Lamy, 1914, Jour, de Conchy., vol. 61, No. 3, p. 303, fig. of hinge on 



p. 302. 

 Cooperella subdiaphana (Carpenter), Dall, 1900, Trans. Wagner Fiee Institute Sciences, 



vol. 3, pt. 5, p. 1062.— Dall, 1921, Bull. 112, U. S. Nat. Museum, p. 145.— Hert- 



lein and Strong, 1948, Zoologica, vol. 33, pt. 4, p. 196; Palmer, 1958, Mem. 



Gaol. Soc. America, No. 76, p. 101, pi. 12, figs. 6-16. 



Shell small to medium-sized (length to nearly 15 mm.), veneriform, 

 convex, thin and fragile, the beaks nearly median, the anterior end rounded, 

 the posterior somewhat narrower. Surface smooth or with fine, concentric 

 lines and slightly undulated, white, shiny, with a play of iridescence. Perio- 

 stracum thin, vernicose, and of a light straw-yellow color. The ligament is 

 external and shows as a small knob behind the beak, the resilium seated 

 in a deep, U-shaped pit floored by the nymph. 



Range — Queen Charlotte Islands, British Colombia, south to San 

 Felipe, east coast of Lower California and near the head of the Gulf of 

 California. 



Cooperella pan^mensls, new sp:cies Plate 84, figure 5 



Shell of medium size, subovate to subquadrate, the umbone prominent 

 and nearly median, subequilateral, the anterior side a trifle higher and 



