34 PALAEONTOLOGY OF CALIFORNIA. 



arise at some distance from the beaks. These are crossed by very 

 tine concentric lines. 



Figure, nearly three times natural size. 



Locality: A single specimen from Gifford's Ranch, Plumas County, California, 

 associated with Ammonites Ramsaueri, Monotis subcircularis, &c. 



TEREBRATULA, Lwyd, Auct. 



T. HUMBOLDTENSIS, n. S. 

 PI. 6, Fig. 35, and 35 a, b. 



Shell oval, elongate, smooth, sides regularly curved; base 

 broadly truncated; lower valve, beaks prominent, incurved; base 

 with a broad, rounded sulcus ; upper valve rounded above, 

 slightly elevated in the middle, below. 



Figures, natural size. All of the specimens are so much distorted that their 

 true outline is almost entirely destroyed. No two specimens are of the same 

 shape, although the one figured appears to be nearly, if not quite, of the normal 

 form. 



Locality: Abundant in Star Canon, Humboldt County, Nevada Territory. 

 Collected by Mr. Homfray. 



RHYNCHONELLA, D'Orb. 



R. LINGULATA, 11. S. 

 PL G, Fig. 36, and 36 a, b. 



Shell plicate, ventricose, sides sloping above, convex below, 

 base subtruncated ; lower valve with three median ribs and three 

 lateral ones on each side ; base sulcate and prolonged into a long 

 tongue-like process, edge serrate ; upper valve with four median 

 ribs, elevated above the general contour of the shell, and three 

 lateral ones alternating with those of the opposite valve. 



Figures, natural size. 

 Locality: With the preceding species. 



Although this shell is also distorted, yet it retains much more completely its 

 normal form than the Terebratula described above. 



