128 University of California Publications in Geology [Vol. 8 



Dimensions. — Length, 23 mm.; height, 37 mm.; convexity, 11mm. 



Occurrence. — University of California localities 781 and 790 near 

 Lower Lake and 1888 near Selby Station. 



Named in honor of Professor Charles E. Weaver of the University 

 of Washington. 



PECTEN (CHALAMYS?), sp. 

 Plate 9, figure 6 



Shell minute, subcireular, equilateral, slightly ventricose. Right 

 valve with exterior surface ornamented by ten squarish ribs, the 

 middle two being decidedly dichotomous; interspaces channeled and 

 about half as wide as ribs; ears nearly equal, markings, obscure. 



Dimensions. — Length, 3 mm. ; height, 2.5 mm. ; convexity, 1 mm. 



Occurrence. — Only one specimen was found, at University of Cali- 

 fornia Locality 790. 



It can be distinguished from all other Eocene pectens on this coast 

 by its small number of external ribs and by the shape of these ribs. 



MODIOLUS BAKERI, n. sp. 

 Plate 9, figure 8 



Shell, medium in size, thick; beak small but prominent, about a 

 sixth of the length from the anterior end which is narrowly rounded ; 

 posterior end, broadly rounded; cardinal margin, straight; ventral 

 margin, slightly rounded; umbonal ridge prominent, rounded, and 

 extending to the posterior end below its center. A marked concavity 

 in larger specimen figured extends from the beaks to the middle of the 

 ventral margin. Surface marked by lines of growth. 



Dimensions. — Smaller specimen : length, 17 mm. ; height, 8 mm. ; 

 convexity, 4 mm. 



Occurrence. — University of California localities 243, near Muir 

 Station, and 1556, lower zone of Martinez north of Mount Diablo. 



This species appears to grow more robust with increase in age. It 

 resembles Modiolus major (Gabb), but its beak is not quite so nearly 

 terminal. The marked concavity on the shell also aids in distinguish- 

 ing it. It differs in shape and in lack of ornamentation from M. 

 ornatus (Gabb). 



Named in honor of Mr. Charles Lawrence Baker, Geologist, 

 Southern Pacific Company. 



