72 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



BRACHIOPODA 



1. Rhynchonella densleonis, sp. no v. 



Plate VII, Figs. 157 and 158. 



Shell of medium size, attaining a diameter of 11-12 mm.; trigonal; gib- 

 bous; when full grown, the greatest convexity being near the middle; poste- 

 rior lateral margins straight, sloping from the beak at an angle of about 

 90 degrees; anterior margin somewhat broadly rounded; dorsal valve more 

 convex than the ventral, nearly globose; ventral valve flattened, though 

 bearing a deep sinus; anterior half of each valve bearing strong, rounded or 

 angular plications which disappear on the posterior portion of the shell; sur- 

 face of both valves bearing fine striations most plainly seen on the posterior 

 half of the shell. The sinus of the ventral valve bears three or four plica- 

 tions, while the corresponding prominence on the dorsal valve bears four or 

 more; beak not very prominent and only slightly curved; deltidium small; 

 width of shell greater than length. 



This species seems to be very closely related to Rhyn- 

 chonella gnathofhora Meek.^ Whiteaves states that R. 

 matidensis Whiteaves^ also resembles Meek's species, and 

 it is therefore not unlikely that the two Cretaceous species 

 are identical. 



Occurrence. — This species is not uncommon at Horse- 

 town, Shasta County, California, in the uppermost beds of 

 this division. In this respect it may also agree with 

 R. matidensts. 



2. Rhynchonella whiteana, sp. nov. 



Plate VII, Figs. 160 and 161. 



Associated with the former species is another somewhat related form, with 

 a finer and more subdued sculpture. The ventral sinus bears about nine or 

 ten plications of uniform size and none of the strong folds of the other. The 

 shell is rather circular in outline. The dorsal valve is crossed by two diverg- 

 ing ridges meeting on the anterior margin the borders of the ventral sinus. 



» Pal. Cat., Vol. I, p. 39, PI. VIII. 

 * Mes. Foss., Vol. I, p. 252. 



