HANNIBAL: CALIFOENIAN FRESHWATER MOLLUSCA. 149 



Sub-genus Walkerola, n. sub-gen. 



Type, Lmix Klamathensis, n.sp. 



Named after Mr. Bryant Walker, whose papers on the American 

 Anctjli have been of much service in working up the Californian forms. 



Sub-genus Walkerola. Shell large, averaging 12 mm. in diameter, 

 patelliform, ovate-elliptical in outline, low-arched, coarsely con- 

 centrically striate, frequently marked internally by an intermittent 

 radiating white - colour pattern, apex medial, ])Osterior scarcely 

 prominent, smooth or marked by concentric striae ; habitat chiefly 

 lacustro-fluviatile, on rocks and the shells of Naiades. 



Sub-genus Latix, s.s. Shell similar to preceding, but decidedly 

 arched and broadly ovate, apex more nearly medial and sub-conspicuous; 

 Walkerola stage completed fairly early during adolescence ; habitat 

 rapid streams, on rocks and other solid objects. 



Lanx (Walkerola) Klamathensis, n.sp. PI. VIII, Fig. 25. 



Ancylus Neivherryi of authors, not of Lea. 



Shell of moderate or large size, fragile, ovate-elliptical, laterally 

 compressed, low-arched, apex sub-central ; habitat lakes and sluggish 

 streams on solid objects. 



Type: max. diam. 11, min. diam. 7-5, alt. 3 mm. Cotype : max. 

 diam. 16, min. diam. 9'5, alt. 3*5 mm. 



Klamath System in basin of Klamath lliver, Oregon. 



Quatei'nary : Summer Lake beds, Oregon. 



Klamath Valley, Oregon : Government Irrigation Dam, Upper 

 Klamath Lake "(types) (E. Applegate, H. Hannibal) ; Upper 

 Klamath Lake (F. M. Anderson) ; Link lliver Rapids, Klamath Falls 

 (K. Applegate, H. Hannibal)^; Klamath lliver, Keno (H. Hannibal); 

 (Quaternary) Summer Lake (F. ^I. Anderson). 



This large low-arched Lanx is doubtless present in various collections 

 under the name of Ancylus JSfeivherryi, Lea, which was described 

 from (Upper) Klamath Lake. A study of Lea's diagnosis and figure 

 and tliat given by Binney make it certain that Newberry, who 

 collected the specimens, really obtained them from one of the streams 

 flowing south from Mount Shasta in California, since they are 

 unquestionably merely finely Aexalo^e^ ([■Ax'k.-coiQw.YQd. Lanx patelloides, 

 and very distinct from the present species. 



Lanx Nuttalli (Ilaldeman). 



Ancylus {Velletea) Nuttalli, Haldeman, 1841 ; A. crassus, Haldeman, 

 1843; A. Kooteniensis, Baird, 1865; A. ^ subrotundatus, Tryon ', 

 Keep, 1888. 

 Shell small, solid, roundly ovate, slightly broader posteriorly, 

 high-arched, apex posterior ; habitat streams. 



Columbia System in Columbia River and tributaries. 



^ One specimen probably washed clown from Upper Klamath Lake above. 



