158 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



jS'car Barsto^v, Mojave Desert, California (J. C. Merriau], C. L. 

 Baker). 



llesembles P. {H/ppeutis) contortus of Europe, somewhat in the 

 nautiliform sliape, but decidedly larger, and lacking the numerous 

 whorls of that species. The absence of apertural lamellae above the 

 periphery on the whorl is peculiar, but characteristic of all the 

 specimens in whicli this character may be made out. 



Flanorlis [Segnioitma) decUvis (Tate), 1870. 



Dall {Alaska, xiii, 1905, p. 98) cites tliis Nicaraguan species from 

 the Umpqua lliver, Oregon. In several years tield-work in California 

 and Oregon the writer has seen nothing corresponding to it, and the 

 species does not appear on a manuscript list of the shells observed in 

 the vicinity of Elkton on the Umpqua River by Fred H. Aiidrus, an 

 old collector. Is this not another Unio Oregonensis ? 



Planoubis (HiPi'KUTis) EXACUTUS (Say). 



Planorhis exaciwus (misprint for exacuhis), Say, 1821 ; P. exacutns, 

 ' Say ' of authors. 



Shell of moderate size, whorls vertically compressed, spire-pit 

 broad for group, umbilicus not appreciably depressed ; habitat ponds 

 and streams. 



American Province. Yukon, Eraser, and Columbia (locally) 

 Systems. 



Loess of Yukon Valley, Alaska. 



Planorbis (Hippeutis) dilatatus (Gould). 



Planorhis lens, Lea, 1838, not of Bronguiart, 1810 ; P. dilatatus, Gould, 

 1841, not of Pfeiffer, 1842; P. lenticularis, Lea, 1844, not 

 of Schlotheim, 1818; P. Btichanensis, Lea, 1844; P. Brong- 

 niartiana, Lea, 1844 ; P. opercularis, Gould, 1847 (syntonic form) ; 

 P. plnnulatus, "W.Cooper, 1860 (syntonic form) ; ?P. '■ gracilentns, 

 Gould', Tryon, 1863; P. Centervillensis, Tryon, 1872; P. callio- 

 glypttis, Vanatta, 4895 (syntonic form) ; P. opercularis, var. 

 Oregonensis, Vanatta, 1895, not P. Oregonensis, Tryon, 1865 = 

 S. trivolvis. Say ; P. opercularis, var. multiUneata, Vanatta, 

 1899; P. Vanvlecki, Arnold, 1910 (syntonic form); P. vermicu- 

 laris of authors in part, not of Gould. 

 Shell small or of moderate size, whorls deep, spire-pit narrow but 



extending to apex, umbilicus not appreciably depressed ; habitat 



lakes and clear streams. 



European and American Provinces. Entire Californian Province 



except Los Angeles and Arizona Systems. 



Quaternary: Lahontan Lake beds, Kevada ; Owens Lake beds and 



alluvial deposits of San Joaquin Valley, California ; Summer and 



Christmas Lake beds, Oregon. Pliocene : Idaho Lake beds, Oregon 



and Idaho ; Kettleman Lake beds, California. 



A common species in the Californian Province, but sporadic else- 



wliere if the records may be depended upon. Besides being reported 



under a variety of names it has doubtless been confused with the 



preceding species, which is less common Avest of the Pock}- Mountains. 



