Vol. VII] DICKERSON— CLIMATE AND OLIGOCENE FAUNAS 171 



Cowlitz River, just back of the Greece ranch house, about four 

 miles east of Vader. Colls., F. M. Anderson and Bruce Martin. 

 Named for Mr. A. B. Reagan, who described several inter- 

 esting Oligocene fossils from Washington. 



Saxicava arnoldi, new species 

 PI. 29, Figs. 5a and Sb 



Shell small, inflated, with thin shell substance; beaks con- 

 spicuous, large, approximate; hinge line nearly straight; an- 

 terior and posterior truncated ; pronounced, oval gaping pos- 

 teriorly ; base arcuate. 



Dimensions: — Length of imperfect type, 12 mm. 



Type: — No. 388, Cal. Acad. Sci. Locality 181, near Vader, 

 Lewis County, Washington, on east bank of the Cowlitz River, 

 just back of the Greeco ranch house, about four miles east of 

 Vader, Colls., F. M. Anderson and Bruce Martin. 



Named for Dr. Ralph Arnold. 



Diplodonta dalli, new species 

 PI. 29, Fig. 8 



Shell medium, inflated, nearly equilateral, equivalve; an- 

 terior dorsal slope slightly concave beneath small inconspicuous 

 beaks, thin, slightly convex; anterior broadly rounded; ventral 

 margin arcuate ; posterior slope nearly straight, sloping steeply 

 to a medial point on posterior half, where it makes well 

 marked angle with the nearly vertical posterior end. A shal- 

 low fluting extends from a point near beak to the middle of the 

 straight posterior end. Concentric incremental growth lines 

 decorate the shell. 



Dimensions: — Length, 22 mm.; height, 23 mm.; convexity,. 

 7 mm. 



Type: — No. 398, Cal. Acad. Sci. Locality 181, near Vader, 

 Lewis County, Washington, on east bank of the Cowlitz River, 

 just back of the Greeco ranch house, about four miles east of 

 Vader. Colls., F. M. Anderson and Bruce Martin. 



Named in honor of Dr. William Healy Dall, whose great 

 works in Conchology and Invertebrate Paleontology will con- 

 tinue to guide students in these subjects for years to come. 



