University of California Publications in Geology [Vol. 9 



The hinge plate is narrow, the ehondophore deep, oval, apically 

 roofed, not overhung by an accessory; cardinal tooth very small, 

 high, situated medially on the hinge plate, arms of equal length, 

 thick, anterior lateral long, low, reaching nearly to the arm of the 

 cardinal. Hinge of the right valve and the pallial sinus unknown. 



This species differs from Mulinia densata in its narrower hinge 

 plate and much smaller cardinal tooth. It is separable from Mulinia 

 pabloensis by the absence of striations on the lateral teeth, and 

 from M. undilifera by its much more delicate teeth. 



The type of this variety was obtained from Miocene strata near 

 Elmer, Chehalis County, Washington. 



Occurrence.— Miocene : Upper Miocene, Elmer, and Satsop, Che- 

 halis County, Washington (Weaver). 



MULINIA UNDILIFERA (Weaver) 

 Plate 34, figures la. lb, 2 and 3 

 Pseudocardium gabbi (Remond) var. undiliferum Weaver, Wash. State 

 Geol. Surv. Bull. 15, p. 69, pi. 9, fig. 76, 1912. 



This variety was described by Weaver as follows : 



Shell typically small, anterior margin slightly convex with a slope of 

 60°; posterior margin nearly straight with a slope of 45°; posterior surface 

 of the shell undulatory because of broad groove extending from the beak 

 to the margin. These characters are constant and do not seem to grade 

 into the other varieties. Several hundred specimens from the same locality 

 show these characteristics. The dimensions of the type are: length, 50 mm., 

 height, 40 mm., convexity, 20 mm. 



The hinge of this species as shown on the type and plesiotype 

 is very heavy, the hinge plate very wide and thick ; ehondophore 

 deep, roofed, but apparently not overhung by an accessory; the 

 left cardinal is partially worn so its height is unknown ; the arms 

 are of equal length, extending ventrally nearly across the hinge 

 plate ; right cardinal not clearly shown in the specimens, the ante- 

 rior arm was probably rather inconspicuous, posterior arm repre- 

 sented by a heavy basal ridge ; laterals smooth, very robust, low ; 

 the anterior one extends for a short distance dorsal to the cardinal 

 arm ; laminae low, the dorsal ones formed entirely from the thick- 

 ened dorsal margin of the shell and not represented by a distinct 

 tooth. The hinge plate at the ventral ends of the laterals is sharply 

 truncated. 



