HANNIBAL: CALIFORNIAN FKESHWATEK MOLLUSCA. 



197 



Yalvata (Tkopidina) thicarixata (Say). 



Cijdostoma tricarinata, Say, 1819 (syntonic form); V. sincera, Say, 

 1824; V. humeralis, Say, 1829; V. hicarinata, Lea, 1841 



(syntonic form); V, striata, Lewis, 1856, not V. striata, Phil., 



1836; V. virens, Tryon, 1863; V. Leioisi, Currier, 1868; 

 V. sincera, var. Cftahensis, Call, 1884 (syntonic fortn) ; J', mergella, 



"Wester kind, 1885; V. Lewisi, var. helicoidca, Dall, 1905; 

 V. humeralis Californica, Pilsbry, 1908 ; V. Calli, Hannibal, 1910 



(syntonic form) ; V. JFhitei, Hannibal, 1910 (syntonic foinn). 



Shell of moderate size for group, turbinate, moderately umbilicate, 

 ■whorls small, sutures well impressed; habitat lakes and larger 

 sluggish streams. 



Sporadically throughout the Xearctic Region and Mexican Province. 



Quaternary : Loess of eastern States ; Pouneville Lake beds, 

 Utah; Lahontan Lake beds, Nevada; Owens Lake beds, California; 

 Summer Lake beds, Oregon; post-Glacial deposits of Vancouver 

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



The present species is readily susceptible to sj'ntonic influences, 

 and as a result varies more or less in the elevation of the spire and 

 breadth of the umbilicus. Extreme forms fre(][uently develop, in 

 addition, one, two, three, or more spiral keels. Upon such a form the 

 original tricarinata was based. V. sincera represents the normal 

 aspect. 



SUMMARY AND RANGE IN TIME OF THE CALIFORNIAN FAUNA.' 



O, present : K, characteristic ; R, recorded from 

 elsewhere, but not from this Province. 



UNIONOIDE^. 



Family MargaritaniDjE. 



Margaritana {Pseiidunio) Herrci, n.sp. . . . 



PI. vii, fig. 17. 

 M. viargaritifera (L.) 



W. Coast Shells, 1910, pi. i, fig. 4. 

 M. viargaritifera falcata (Gould) 



AlasDwdon falcata, Gould, Wilkes Exp. 

 Moll., figs. 54.5fl, b. 



Family Unionid.e. 



Unio transpacifica, Arn. & Hann., n.sp. 



PI. vii, fig. 18. 

 Migranaja Condoni (White) 



L"nioCo)irfoni,White,Bull.l8U.S.G.S.,pl.ii. 

 Anodonta cygnca impura (Say) 



PI. V, figs. 1, 2. 

 A. ci/gnea (L.) 



PI. V, figs. 3, 4. 



O 



I O 



See note on p. 211. 



