196 PKOCEKDINGS OF TIIIC ilA I,ACOT,OGICAL SOCIETV. 



LioPLAX Andkrsoniana, 11. sp. V\. VITT, Fig. 33. 



Shell of moderate size, similar to A. suhearinata, but more slender, 

 rcij;nlarly elevated-conic, sub-perforate, whorls not deej), strongly 

 inriated, and indistinctly shouldered at periphery, aperture slightlv 

 sinuate ; luibitat apparently lacustrine. 



Altitude 21, diameter 11, altitude of aperture 9 mm. 



Eocene: local freshwater beds in Tejon formation, California. 



Corral Hollow, near Tesla, California; cut along Western Pacific 

 Railroad, one-quarter of a mile above Carnegie Pottery plant (tvpes) 

 (H. Hannibal) ; same locality (vStanford TJtiiversity Geological Survey, 

 ])er W. H. Ochsner) ; mouth of long gulch from north, three-quarters 

 of a mile above Carnegie Pottery plant (Stanford University Geological 

 Survey, per J. R. Pemberton) (H. Hannibal). 



Xamed after Mr. Robert Anderson, of the United States Geological 

 Survey. 



Superfamily VALVATOIDE^ (Gray), 1840. 



Family YALYATID^, Gray, 1840. 



Shell small or minute, planorbiform or tuibinate, umbilicate, 

 whorls iiormallj' round, sutures impressed, aperture circular not 

 oblique, peristome complete, operculum corneus and multispiral; 

 animal oviparous, muzzle produced, tentacles filiform, branchiae 

 plumose-pectinate and exposed on right side, foot sub-quadrate and 

 bilobed in front ; habitat lakes. 



The family contains but the one widespread genus, Vahata, of 

 which a single protean species inhabits North America. 



Genus Valvata, Miiller. 



Vahata, Miiller, 1774 ( F. cristaf.a, ^liill.); Gyrorlis, Fitzinger, 

 1833 {V. cristata, Miill.) ; Flanella, Schliiter, 1838 ( T. cristata, 

 Miill.); Flanorbitina, Betta, 1868 ( F. cridata, Miill.). 

 Tvpe, Valvata cristata, Miiller. 



Sub-genus Teopidina, H. & A. Adams. 



Ci/clostoma (sp.), Say, 1819 ( C. tricarinata. Say); Tropidina, 

 H. & A. Adams, 1854 (C. tricarinata, Say); Cincinna, Morch, 

 1863 ( V.piscinalis, Miill.); ValvatineUa, Betta, 1868 ( V.piscinalis, 

 Miill.); lelshia, Bourguignat, 1877 {V. je Is kii, Crosse) ; Jelskia, 

 Westerlund, 1886 (emended form), not Jelskia, Taczanovich, 

 1871. 

 Type, Cjjclostoma tricarinata, Say. 



Sub-genus Valvata, s.s. Shell minute, averaging 2 mm. in breadth, 

 planorbiform, widely umbilicate, sutures moderately impressed; 

 habitat lakes. 



Sub-genus Tropidina. Shell prevailingly larger than Valvata, s.s., 

 averaging 4 mm. in breadth, turbinate, narrowly or moderately 

 umbilicate, sutures deeply impressed ; Valvata stage carried back to 

 eaily adolescence ; habitat lakes. 



