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University of California Publications in Geology [Vol.11 



extending from the beaks to the posterior end and enclosing a secondary escutcheon 

 which is more sharply limited and more strongly depressed than the primary one. 

 Surface of shell sculptured by numerous fine concentric ribs. On the surface 

 near the posterior dorsal edge there is a shallow groove which extends from the 

 beaks to a little anterior to the posterior end. Hinge plate unknown. 



Dimensions. — Type specimen: Length, 12 mm.; height, 7 mm. 



Occurrence. — University of California localities 1131 and 2754. Type from 

 locality 1131. 



This form is somewhat like L. taphra Dall, 93 a Recent West Coast 

 species. It differs from that species in that it is slightly more 

 elongate, and the concentric sculpturing is somewhat finer. The 

 most important difference, however, is the presence of the double 

 escutcheon ; on L. taphra the escutcheon is single. 



L. pulchrisinuosa somewhat resembles L. gabui Conrad, 94 common 

 in the Eocene of the West Coast : it differs from that species prin- 

 cipally in that it is not so acute and elongate posteriorly, also in that 

 the sculpturing is somewhat finer. 



L. pulchrisinuosa is also somewhat similar to L. oschineri Ander- 

 son and Martin, 95 a species described from the Monterey of Kern 

 County. The latter species differs from the former in being more 

 acute anteriorly and posteriorly; the sculpturing is coarser, and the 

 lunule and escutcheon are larger. The escutcheon of the latter species 

 has the double area seen on the former, but the secondary escutcheon 

 on L. oschineri is larger than that of L. pulchrisinuosa. 



LEDA KAMONENSIS, n. sp. 

 Plate 12, figure 9 

 Type specimen no. 11167, Coll. Invert. Palae. Univ. Calif., loe. 1131 

 Shell small; beaks nearly central, rather inconspicuous; angle of dorsal slopes 

 fairly low, almost equal; both dorsal slopes straight and nearly equal in length. 

 Posterior end acutely rostrate ; anterior end regularly rounded. Lunule lanceolate, 

 narrow and not very long ; escutcheon elongate-lanceolate, reaching over two- 

 thirds the length of the posterior dorsal edge, slightly pouting. Surface of shell 

 covered by regular, well-marked concentric lines. 



Dimensions. — Type specimen : length, about 16 mm. ; length of beaks from 

 posterior end, about 9 mm. 



The writer at first considered this form to represent immature 

 individuals of Yoldia cooperi tenuissimu, which is common in the 



93 For original description of Leda taphra see Bull. Nat. Hist. Soc. Brit. 

 Columbia, no. 2, p. 7, pi. 2, figs. 6, 8, 1917. For a good redescription and figure of 

 Leda taphra Dall see Mem. Calif. Acad. Sci., vol. 3, p. 98, pi. 17, fig. 5, 1903. 



94 For good figure of type specimen of Leda gabbi see Geol. Surv. Calif., 

 Palaeontology, vol. 1, pi. 26, fig. 185. Gabb listed it as Leda protexta? It was 

 renamed by Conrad. 



95 For original description of Leda oschineri see Proc. Cal. Acad. Sci., ser. 4, 

 vol. 4, p. 53, pi. 3, figs. 8a-c, 1914. 



