266 PROCEEDINGS OF THE CALIFORNIA 



Genus Porapholyx, Lea. 

 Proc. Phil. Acad., Ap. 1st, 1856. 

 Type P. effusa Lea, sp. unica. [Fig. 28.] 

 Fin. 28. Shell ; small, swollen, with three whorls, the last much the largest. 

 Above, rounded planulate, suture deep but not channelled. Below, 

 not umbilicated, rounded convex. Aperture large, effuse, internally 

 shining. Columella flattened, not folded ; externally, in fresh speci- 

 mens, greenish horn color ; dead ones nearly white or waxy brown. 

 Alt. 0.14 in., major diam. 0.2, min. diam. 0.16 in. 



Soft parts. Foot rounded truncate, short, bluish-ash color, darker 

 on the margin. Lips broad, semilunar. Tentacles long, eyebearing ; 

 tips pale yellow, eyes black ; a second pair sessile on the inner bases 

 of the tentacles. Body delicate brownish olive green; a light 

 streak just behind and outside of base of each tentacle. 

 Localities: Sacramento River (Trask), Lea ; Eagle Lake, Horn ; Klamath 

 Yalley and Frazer Spring, Gabb. 



I am indebted to Mr. Win. M. Gabb, of the State Geological Survey, for 

 notes and drawings, confirmatory of previous doubts in regard to this rare and 

 interesting raollusk. They were taken from the living animal, and coming from 

 a distinguished Palaiontologist may be relied on as correct. 



[N.B. — Through inadvertence in drawing, the shell is represented as reversed in the 

 figure.] 



Professor Whitney made some remarks on the geology of the 

 State of Nevada, of which the following is an abstract. 



Having recently received a small but very interesting collection of fossils, 

 made in Nevada by Mr. J. E. Clayton, the examination of which has added 

 considerably to our scanty stock of information in regard to the geology of an 

 extensive region comprised between the meridians of 115° and 120°, and the 

 parallels of 38° and 41°, I take this occasion to set forth, in a very concise 

 manner, the information which I have collected, up to the present time, in regard 

 to the age of the sedimentary formations of the regions in question. 



The State of Nevada occupies a portion of the continent which, during the 

 last few years, has received a large share of attention from the public and ex- 

 cited the greatest interest among scientific men ; but where, up to the present 

 time, detailed geological work has been impossible, owiug to the absence of any 

 geographical map of the State approaching even to accuracy. 



The U. S. Pacific Railroad Surveys furnished no geological information 

 whatever in regard to the territory embraced within the present area of the 

 State of Nevada. The route from Salt Lake to Humboldt River, at Lassen's 

 Meadows, was hastily explored by Captain Beckwith, in May, 1854, and he was 

 accompanied by Mr. Schiel as Geologist ; but no information of any value is 

 'given in regard to the geological structure of the region traversed by the party, 



