HANNIBAL: CALIFORNIAN FEESHWATEK MOLLUSCA. 127 



Sub-genus Limnobasilissa, n. sub-gen. 

 Margaritana (sp.), J. G. Cooper, 1894 {M. stibangtdata, J. G. C). 



Type, Margaritana sribangidata, J. G. Cooper. 



Sub-genus Limnobasilissa. Shell of moderate size, averaging 60 mm. 

 in length, margaritaniform, sub-solid, elongate-quadrate, rounded in 

 front, obliquely truncate behind, postero-ventral margin barely acutely 

 angular, posterior slope sub-rounded, beaks marked by several wavy 

 ridges which make an abrupt bend on crossing the postero-ventral 

 slope, early growth similar in outline to adult, liinge with a reduced 

 clavate pseudo-cardinal in eacli valve, hinge-line sinuate in trout of 

 umbones ; habitat lacustrine. 



Sub-genus Gonidea, s.s. Shell of moderate size, similar to Limno- 

 hasilissa, but anodontiform, more or less elongate-trigonal and anteriorly 

 pointed, posterior slope more or less carinate, hinge with an obsolete 

 pseudo-cardinal in each valve or edentate, but slightly sinuate in front 

 of umbones ; Limnohasilissa stage carried back to early adolescence ; 

 habitat fluviatile. 



Gonidea (Limnobasilissa) angdlata subangulata (J. G. Cooper). 



Margaritana subangulata, J. G. Cooper, 1894; G. Coalingensis, Arnold, 

 1910 (syntonic form) ; G. Coalinge?isis, xar. Cooperi, Arnold, 1910. 



Shell of moderate size, elongate-quadrate, compressed, of about 

 equal width posteriorly and anteriorly, rounded in front, rather 

 squarely decurtate behind, postero-ventral slope barely angular ; 

 beaks low, hinge with a reduced pseudo-cardinal in each valve ; 

 habitat apparently lacustrine. 



Pliocene : Kettleman, Santa Clara, and Cache Lake beds, California. 



Gonidea angulata. (Lea). 

 Anodonta angulata, Lea, 1838; Anodon feminalis, Gould, 1850; 

 A. Rand alii, Trask, 1855; A. biangulata, Sowerby, 1869. 



Gonidea angulata Haroldiana, Dall. PI. YI, Fig. 2. 

 Anodonta angulata, var. subangulata, Hemphill, 1891, not Anodon(ta) 

 subangulata, Anthony, 1865; G. angulata, var. Ifaroldiana, 

 Dall, 1908. 



Shell of moderate size, elongate-quadrate, rather compressed, some- 

 what broader posteriorly, rather obliquely truncate behind, postero- 

 ventral slope exhibiting a rudimentary carina, beaks barely elevated, 

 liinge with a very obsolete pseudo-cardinal in each valve ; early 

 adolescent stage as in mature subangulata; habitat quiet rivers, creeks, 

 and sloughs. 



Fraser, Columbia, Klamath, Coast Range, and Los Angeles Systems. 



G. angulata. Shell of moderate size, elongate-trigonal, stronglj- 

 inflated in the region of the postero-ventral ridge, which is sharply 

 carinate, giving the shell an appearance of being cut off abruptly 

 behind, pointed anteriorly, broad and obli(iuely truncate posteriorly, 

 beaks somewhat elevated, hinge edentate and but slightly sinuate ; 

 shell similar to Haroldiana at mid-adolescence, to subangulata in very 

 young stages ; habitat rivers and brisk streams. 



VOL. X. — JUNE, 1912. 9 



