170 CALIFORNIA ACADEMY OF SCIENCES. 



The shells were crushed flat, but their outlines were so 

 perfect and white in contrast with the black shale, that I 

 had no difliculty in making perfect tracings of them. 

 The engraver for the Mining Bureau took the liberty of 

 trying to restore the surfaces, but it is evident that such 

 crushed shells could not be properly represented as given 

 in that report. Still there was no appearance of any sur- 

 face characters except lines of growth. The figures are 

 of natural size. 



Tassajara Lake? Bed. 



Along a small branch of Walnut Creek, in Alameda 

 County, north of Livermore, is a deposit which contains 

 chiefly living species, and was formerly called quater- 

 nary^, but one extinct species has been described from 

 there, and its high elevation, nearly corresponding with 

 the bed last described, makes it probable that it may bet- 

 ter be called pliocene. The species were mostly given 

 in the Catalogue of California Fossils, compiled by me 

 for the State Mining Bureau's report of 1888. 



1. Bythhiella hinneyi Tryou. 6. Limnophysa hiimilis Say. 



2. Carinifex neioberryi l-iea,. 7. Limnophysa pcdustris lAnn^ . 



3. Gochliopa roiueUP. Tryou. (See 8. Liinnophysa desidiosaSay. 



Pompholopais.) 9. Menetus opercularis dowld. 



4. Gyraulus vermicularis Gould. 10. Physa diaphana Tryou. 



5. Helix calif orniensis I-iea., \ai's. 11. Pisidium oceidentale'Se^'C. 



12. Pompholopsis ichiici Call. 



The last may be what I called Cochliopa rowelli, as my 

 specimens agreed nearest with the figure of that species 

 in Binney's work. It is also possible that some of the 

 living species from horizontal beds along the creek are 

 quaternary, being also found living in the creek, and now 

 being fossilized, but others do not now live there. Sur- 

 veys have not been made to determine whether the fossil 

 beds extend up the hill slopes. 



