56 PALAEONTOLOGY OF CALIFORNIA. 



ent form is much more common than the short rounded one previously figured by 

 me. It has a strongly characterized Mercenaria hinge, and is the only species of 

 that genus yet known on the Pacific coast, unless Eeeve's and Conrad's species 

 should prove distinct. 



CARYATIS, Roem. 



C. Barbarensis, n. s. 



PI. 15, Fig. 15, 15 a. 



Shell rather small, transverse, gibbous, thin, inequilateral; 

 beaks subcentral, small, strongly incurved, umbones prominent; 

 outline broadly excavated under the beaks, the anterior end pro- 

 duced and narrowly rounded ; posterior end narrow; base irregu- 

 larly rounded, strongly curving upwards anteriorly; posterior 

 cardinal margin sloping with a slight, but regular curve. Hinge 

 delicate; teeth small. Surface covered by irregular striae of 

 growth. Lunule very large, occupying all the space from the 

 beaks to the anterior end, and bordered by an impressed line. 



Length, 1.5 inch ; width, 1.1 inch ; height of a single valve, .4 inch. 



The only shell on the coast, to which this has the most remote resemblance is the 

 young of Amiantls callosa (Cytherea id. Con.) It can, however, be at once dis- 

 tinguished by its longer form, narrower at both ends, its greater convexity, its 

 being much more deeply excavated under the beaks, and by the surface being 

 marked only by lines of growth, instead of concentric ribs. 



A single specimen was found in the Pliocene of Santa Barbara. 



MERETRIX, Lam. 



M. Traskii, Con. sp. 



(Lutraria Traskii, Con., P. E. E. Eep., Vol. 5, p. 324, pi. 3, fig. 23.) 



This shell is peculiar to the white or Bituminous Shales of the Upper Miocene. 

 It was described by Mr. Conrad from casts in this rock. I have been fortunate 

 enough to see the cast of the hinge of both valves, and find that it is a Venerid, and 

 appears to belong to the above genus. It is rather rare, but seems to be most 

 abundant in the immediate vicinity of Monterey. 



