Vol. IV] DICKERSON—SIPHONALIA ZONE, OREGON -^^7 



PITARIA MARTINI, new species. 

 Plate 11, figures 2a, 2b, 2c. 



Shell of moderate size ; elongate, with beaks slightly anterior 

 of the center; anterior dorsal margin somewhat concave; the 

 slightly convex posterior dorsal margin sloping less steeply 

 than the anterior margin; anterior end sharply rounded; pos- 

 terior end narrowly rounded; ventral margin convex, fluted; 

 a marked umbonal ridge extending to a point on the ventral 

 margin two-fifths of the distance from the posterior end; a 

 shallow groove running posteriorly, and parallel to the um- 

 bonal ridge; lunule long, narrow; escutcheon indistinct. 



Dimensions : Height, 32mm ; length, 42mm. 



Type: — No. 237, and cotype. No. 238, California Academy 

 of Sciences. Locality 25, Roseburg Quadrangle, Oregon, near 

 the center of Sec. 19, T. 26 S., R. 3 W., on the east bank of 

 Little River at its confluence with the Umpqua, underneath 

 the bridge at that point. 



Named for Mr. Bruce Martin, sometime Assistant Curator 

 of Paleontology, California Academy of Sciences. 



TIVELA WEAVERI, new species. 

 Plate 11, figures 3a, 3&, 3c. 



Shell trigonal, with beak central, equivalve; the nearly 

 straight anterior margin sloping steeply to a narrowly rounded 

 anterior end; the slightly convex posterior margin sloping al- 

 most as steeply as the anterior ; posterior end rounded broadly ; 

 base broadly rounded; hinge of right valve exhibiting three 

 strong cardinals and a socket for a lateral in the anterior por- 

 tion of hinge plate; pallial sinus appearing to be a small V- 

 shaped one ; lunule and escutcheon indistinct. 



Dimensions: Height, 29mm; width, 31mm. 



This species resembles Crassatellites grandis (Gabb) in gen- 

 eral form. Its shell and hinge plate are not nearly so heavy as 

 those of C. grandis. Common at localities 24 and 25. 



Type :— No. 239, and cotype. No. 240, Cal. Acad. Sci. Lo- 

 cality 25, Roseburg Quadrangle, Oregon, near the center of 

 Sec. 19, T. 26 S., R. 3 W., on the east bank of Little River at 

 its confluence with the Umpqua, underneath the bridge at that 

 point. 



Named in honor of Professor Charles E. Weaver of the Uni- 

 versity of Washington. 



