150 PROCEEDINGS OF THE MALACOLOGICAL SOCIKTY. 



Lanx TATELLOiDEs (Lea). 



Anci/1 US patella ides, Lea, I806; A. Newberry i, Lea, 1858; A. alius, 

 Tryou, 1865. 



Shell large, sub-solid, broadly ovate-elliptical, broader posteriorly, 

 moderately regularly conical, apex sub-ceutral ; habitat on rocks iu 

 streams. 



Klamath System iu streams draining into Sacremento lliver. 



Lanx scbuotundatus (Tryon). 



Aucylus suhrotundatus, Tryon, 1865; A. patelloides and A. Newherriji 

 of authors, not of Lea. 



Shell large, sub-solid, roundly ovate in outline, slightly broader 

 posteriorly, moderately arched, the antei"ior and posterior slopes gently 

 rounded, apex sub-posterior ; habitat streams. 



Columbia System in Umpqua lliver and tributaries. 



Very similar to patelloides, but less regularly conical, and the apex 

 distinctly posterior. 



Genus Ljevaimcx (Walker). 

 Lfcvapex, Walker, 1903 {A./uscus, C. B. Ad.). 

 Type, Ancylus fuscus, C. B. Adams. 



Sub-genus Ferrissia, "Walker. 

 Ancylus (sp.). Say, 1819 {A. rivularis, Say); ? ITaldemauia, Clessin, 

 1888 (A. ohscurus, Hald.), not Haldemania, Tryon, 1862; 

 Ferrissia, Walker, 1903 {^A. rivularis, Say). 



Type, Ancylus rivularis. Say. 



Sub-genus LcBvapex, s.s. Shell of moderate size for group averaging 

 8 mm. iu diameter, patelliform, low-arched, broadly ovate-elliptical 

 in outline, finely radially and concentrically striate, apex sub-dextral, 

 barely posterior, not prominent, and marked only by concentric 

 strife ; habitat chiefly lacustrine. 



Sub-genus Ferrissia. Shell similar to preceding, but of smaller size, 

 averaging 5 mm. in diameter, patelliform, ovate-elliptical in outline, 

 arched, finely radially and concentrically striate, apex hardly 

 prominent, sub-posterior, and marked by fine concentric and sub- 

 spirally radial stride ; Lcevapex stage completed during early adolescence ; 

 habitat chiefly streams, less frequently in lakes and ponds. 



L.evapex (Ferrissia) caurixcs (W. Cooper). 



Ancylus caurinus, W. Cooper, 1860 (nude name), in Binney, 1865, 

 figure; A. 'fragilis, Tryon', Tryou, 1872; A. ' patelloides, Jjea', 

 J. G. Cooper, 1872; A. Oreyoiiensis, Clessin, 1881; A. caurinus 

 subalpinus, J. G. Cooper, 1892 ; A. rivularis of authors, not of 

 Say ; not^. ^caurinus. Coop.', J. Henderson, 1907 = Z. rivularis. 

 Shell of moderate size, somewhat elongate, ai'ched, apex sub- 

 posterior, not prominent ; habitat streams and ponds on subraeiged 

 vegetation. 



Fraser, Columbia, Utah, Nevada, and Klamath Systems. 



