154 PALEONTOLOGY OF CALIFORNIA. 



LUTRARIA, Lam. 



L. TRUNCATA, 11. S. 

 PI. 22, Fig. 128. 



Shell thin, compressed, somewhat elongated, length compares 

 with the breadth as about four to three ; beaks nearly central, 

 prominent, small, acute and slightly inclined forwards ; anterior 

 cardinal margin slightly sinuous, posterior convex, nearly straight; 

 anterior end rounded; posterior obliquely truncated, gaping. 

 Surface marked by faint, irregular lines of growth. 



Figure, natural size. 



Localities: Pence's Ranch, Butte County, collected by Mr. Ashburncr. Also at 

 Cbico Creek (from Division A.). 



ASAPHIS, Modeer. 



A. UNDULATA, 11. S. 

 PI. 22, Fig. 129. 



Shell minute, oval, convex, very thin ; beaks small, nearly 

 central, and prominent; posterior cardinal line regularly con- 

 vex, anterior slightly excavated; extremities round and equal; 

 basal margin broadly and regularly convex. Surface marked by 

 minute, equal, concentric lines (about 5 or 6 in .01 inch); and at 

 the two ends by a few large radiating ribs or undulations ; these 

 are most marked on the posterior end, and are entirely absent on 

 the middle half of the surface. Hinge small, the bifid tooth of 

 the left valve being only represented by two minute tubercles. 



Figure, magnified a little more than three times. 



Locality : From the lower beds, Texas Flat, Placer County ; collection of the 

 California Academy of Natural Sciences. 



