204 PALAEONTOLOGY OF CALIFORNIA. 



The locality is on one of the branches of Eel Kivcr, at the mouth of Salt Creek, 

 southwest of Round Valley, Mendocino County 



The species is remarkable for its thin, flat shell, often distorted, and for its broad, 

 flat hinge. 



BRACH10PODA. 



RHYNCHONELLA, Fisch. 

 R. WHITNEYI, Gabb. 



PI. 34, Fig. 105, a, b. 



(Terebratella Whitneyi, Gabb ; Pal. Cal., Vol. 2, p. 35, pi. 12, fig. 62, 62 a.) 

 (Compare R. joeregrrina, Von Buch sp., d'Orb. ; Pal., Fr. Terr. Cret., Vol. 4, p. 16, 

 pi. 193.) 



"When this species was described, it was supposed to be Tertiary, and the descrip 

 tion and figures were taken from immature specimens. In the latter part of 1866 

 I had an opportunity of studying the rocks from which it came, and found them 

 interstratified with shales containing Aucella Piochii and Belemnites impressus, 

 thereby proving them to belong to the Shasta Group. The species is extremely 

 abundant in the white limestones of Lake and Colusa Counties, and I was fortunate 

 in procuring the large specimen now figured. The species is very closely allied to 

 R* peregrina of the French Neocomien, and it is not impossible that they may 

 yet prove identical. I shall, however, retain the specific name for the present, 

 until the question of their identity can be definitely settled pro or con. The follow 

 ing points of difference exist between the specimen before me, and a fine example 

 of the French shell in the Museum of the Philadelphia Academy. "While the 

 number and shape of the ribs are the same in both specimens, the Californian shell 

 is very much more convex, the beak is higher, and the deltidium is markedly 

 narrower ; in R. peregrina, all of the ribs which reach the lateral margins cause* a 

 strong zigzag serration of the margin when viewed directly ; in the present shell, 

 this effect is produced only below the middle, on account of the upper ribs becoming 

 less distinct as they approach the edge. 



Very numerous specimens of another Brachiopod have been found by Mr. 

 Mathewson at Martinez, in a sandstone, probably of the Chico Group The valves 

 are always separated, and I have never succeeded in discovering a single generic 

 character. The shell is very transverse, a third wider than long, and is closely 

 covered by minute radiating ribs to beyond the middle, where, reversing the usual 

 order, instead of branching they unite by twos or threes, forming a few large 

 angular folds on the lateral and basal margins. One valve appears to have a broad 



