1916] Packard: Mcsozoic and Cenozoic Mactrinae 309 



The general shape is stated to be quite constant, especially as 

 regards the posterior flexure. The hinge of the few specimens 

 observed seem quite constant and sufficiently different from any 

 other species or variety to deserve specific rank. 



This species might be confused with M. dcnsata or M. alia, but 

 it is readily separable from either of these upon the basis of its 

 unique type of dorsal laminae and its robust laterals. 



The type of this species was obtained from Sylvia Creek, Che- 

 halis County, Washington. 



Occurrence. — Miocene : Upper Miocene of Sylvia Creek, Chehalis 

 County, Washington (Weaver). 



MULINIA LANDESI (Weaver) 



Pseudocardium latidesi Weaver, Wash. State Geol. Surv. Bull. 15, p. <>!•, 

 pi. 9, fig. 75, 1912. 



This species was described by Weaver as follows: 



Shell thick, equivalve. nearly equilateral; anterior and posterior margins 

 sloping steeply and at about the same angle; base evenly rounded; beaks 

 prominent and pointing slightly forwards; escutcheon narrow but fairly 

 well defined. Surface ornamented with heavy concentric lines of growth; 

 hinge moderately heavy. The dimensions of the type are: length, 45 mm., 

 height, 53 mm., convexity, 25 mm. 



The writer has not seen the type of this species. It comes from 

 the same collecting locality as did the species M. undilifera and it 

 may represent but a ventricose form of that variety. 



The type of this species was obtained from Sylvia Creek, Che- 

 halis County, Washington. 



Occurrence. — Miocene : Upper Miocene of Sylvia Creek, Chehalis 

 County, Washington (Weaver). 



MULINIA PABLOENSIS, n. sp. 

 Plate 34, figures 4a and ib 

 Shell rather ventricose, nearly equilateral, umbones usually pos- 

 terior to the middle of the shell; anterior dorsal edge nearly straight, 

 excavated in front of the beaks ; anterior extremity rounded to sub- 

 truncate ; posterior dorsal edge slightly convex, extremity strongly 

 truncated ; some specimens show a posterior umbonal ridge, which is 

 imperfectly seen in the type ; base broadly arcuate. Surface rough- 

 ened by numerous irregular lines of growth. Pallia! sinus shallow; 



