160 The Molluscau Family Planorhidae 



Geological Horizon and Distribution. Eocene, Triickee Lake beds, 

 Nevadci; Payette Lake beds, Idaho; Fossil Hill, Kawsoh Mts., Nevada; 

 Pliocene, Cache Valley, Mendon, Collinston, Utah; Tulare formation, 

 Kettleman Hills, California; Warner Lake beds, eastern Oregon. A single 

 species, Vorticifex stearnsii (White) has been reported from the INlorrison 

 formation in Wyoming, belonging in the upper Jurassic or Lower Creta- 

 ceous period. 



Species Considered as Valid. The following species and races have 

 been referred to this genus. 



Vorticifex tryoni (Meek) Vorticifex binneyi (Meek) 



Vorticifex tryoni concava (Meek) Vorticifex stearnsii (White) 



Vorticifex tryoni ventricosa (Meek) 



Remarks. Vorticifex appears to be a rather distinct genus related to 

 both Carinifex and Parapholyx. Tlie wide body-whorl with its distinct 

 costae is ciuite characteristic. The name Paradines Dall (1924, p. 112) 

 founded upon the larger species Carinifex binneyi IVIeek does not appear 

 more than specifically distinct from the smaller Carinifex tryoni Meek. 

 Both species seem, from the published figures, to be generically closely 

 related and to be distinct from the genus Carinifex. 



Several species referred to "Vorticifex appear to belong elsewhere. 

 Vorticifex sanctaeclarae Hannibal and V. sanctaeclarae marshalli Arnold 

 seem rather to belong in Carinifex as originally described rather than in 

 Vorticifex as listed by Henderson (1935, p. 257). They were placed in 

 Carinifex by Pilsbry (1934, p. 567). Tlie Vorticifex laxus of Chamberlin 

 and Berry (Nautilus, XLVH, p. 26, 1933) does not appear to fit into the 

 genus Vorticifex, but might be included in the genus Carinifex. It appears 

 to be an internal cast and the external characteristics would not show 

 clearly in such a condition. 



Genus PERRINILLA Hannibal, 1912 

 Type by original designation Helisoma cordillerana Hannibal 



1912. Perrinilla Hannibal, Proc. Mai. Soc. London, X, p. 159. Type Helisoma cordil- 

 lerana Hannibal. As subgenus of Helisoma 



1923. Perrinilla Wenz, Fossil. Cat., Pars 22, p. 1518. Genotype Planorhina (Perrinilla) 

 cordillerana (Hannibal). As subgenus of Planorhina Haldeman 



1934. Perrinilla Pilsbry, Proc. Acad. Nat. Sci. Phil., 86, p. 48. Type Helisoma cordil- 



lerana Hannibal. Presumably considered as genus 



1935. Perrinilla J. Henderson, Fossil Non-Marine Moll, of N. A., p. 246. Type 



Helisoma cordillerana Hannibal 



Shell (plate 79, figs. 31-32). 'Similar to Planorbella, except that it is 

 totally ultra-sinistral; spire-jiit deep and narrow, umbilicus but slightly 

 excavated, superior and inferior peripheries subangular' (Hannibal for 

 subgenus). 



'Shell of considerable size, whorls large, somewhat compressed, and 

 strongly ultrasinistral, the umbilicus barely concave, superior and in- 

 ferior periplicries subangular in young stages, becoming rounded in adult, 

 growth striae strong, spiral striae occasionally preserved, aperture ex- 

 panded somewhat in adult; habitat apparently lacustrine. Diameter 22, 

 alt. 9, diameter of aperture 12 mm.' (Hannibal, p. 161, description of 

 Helisoma cordillerana) . 



