154 University of California Publications in Geology [Vol. ll 



valve covered by concentric lines, which are somewhat finer and closer together 

 than on right valve ; posterior dorsal margin not so strongly depressed as on right 

 valve. On the depressed margin there is a shallow sinus, which is not separated 

 by a distinct ridge from the surface anterior to it. 



Dimensions. — Length, about 44 mm.; height, about 27 mm. 



Occurrence. — University of California locality 1131, outcrop in bed of creek 

 about one-half mile south and a little west of the town of Walnut Creek. 



T. tenuilineata resembles rather closely T. idea Dall, 122 a Recent 

 West Coast species ; the two are somewhat different in outline ; the 

 beaks of the latter are more conspicuous ; the raised concentric lines 

 are somewhat coarser and on the posterior margin they appear to be 

 more strongly imbricated. T. tenuilineata lacks the fine radiating 

 lines seen on T. idea. 



Genus MACOMA Leach 

 MACOMA, aff. NASUTA Conrad 

 This species was listed by the writer 1 - 3 in a former paper as 

 Macoma nasitta; a further study of better material, obtained at the 

 same locality from which it was previously listed, shows that it is a 

 distinct form, the principal characters that distinguish it from M. 

 nasuta being that the beaks are possibly more anterior, the posterior 

 dorsal margin is longer and the posterior end more acute. The speci- 

 mens at hand, representing this form, are so poorly preserved that it 

 does not seem best to give it a specific name ; the writer is of the 

 opinion, however, that it may be a new species. 



Occurrence. — University of California locality 1900, near the top of the 

 Kirker formation. 



Genus METIS H. and A. Adams 

 METIS ROSTELLATA, n. sp. 

 Plate 9, figure 7 



Type specimen 11120, Coll. Invert, Palae. Univ. Calif., loc. 1131 

 Shell medium in size, ventricose, equivalved, broadly subrostrate posteriorly, 

 broadly rounded in front ; beaks rather inconspicuous, situated within the anterior 

 third of the shell. Anterior dorsal edge very short, gently convex and with no 

 angulation or change in slope between it and the rounded anterior end; posterior 

 end narrow, broadly truncate. Surface rather strongly excavated just anterior 

 to the beaks ; covered by low, sharp, somewhat irregular lines of growth. Posterior 

 dorsal margin on left valve strongly depressed and separated from main portion 

 of shell by a distinct ridge, which reaches from the beak to the posterior end ; 



122 For original description of TeUina idea, see Dall, W. H., U. S. Nat. Mus., 

 vol. 14, p. 183, pi. 6, fig. 3; pi. 7, figs. 1, 4, 1891. 



123 Clark, B. L., The Neocene section at Kirker Pass, on the north side of 

 Mount Diablo, Univ. Calif. Publ., Bull. Dept. Geol., vol. 7, no. 4, p. 51, 1912. 



