I08 ALASKA GEOLOGY 



it is less arcuate and subtruncate terminally behind ; but it shows the 

 hinge of Tellina with well developed anterior and posterior lateral 

 laminae. The surface appears to have been nearly smooth. The shell 

 is more convex than one expects a Tellina to be, recalling in this re- 

 spect the species of Psammacoma which have no lateral teeth. It 

 has a length of 24, a breadth of 12, and a diameter of about 5 mm. 



Spisula callistaeformis sp. nov. 



Pl. IX, fig. 9. 



Shell elongate, recalling Macrocallista in outline, the anterior end 

 slightly shorter, attenuated and rounded in front, arcuate below, wider 

 and rounded behind with an obscure radial ridge near the dorsal slope ; 

 disk slightly flattened, concentrically striated, the beaks pointed and 

 moderately elevated. Length 50, height 28, diameter about 16 mm. 



Locality. Upper beds, 3373. 



This species is rather abundant and uniform. The pallial sinus is 

 deep and free from the pallial line for most of its length below. The 

 hinge as far as observable is that of Spisula or Cymbophora. 



Spisula sp. 



Localities. Upper beds, 3375 and 3376. 



This species, though represented by very inferior specimens, is ob- 

 viously more convex, more trigonal, and had a heavier shell than 5". 

 callistceformis. The pallial sinus in one specimen is decidedly shorter 

 and more angular than in that species. 



Mesodesma alaskensis sp. nov. 



Pl. IX, fig. I. 



Shell solid, heavy, nearly smooth with a few feeble concentric lines, 

 very inequilateral ; the beaks low, blunt ; the anterior end long, 

 rounded behind, with a nearly straight base and a short bluntly trun- 

 cate posterior end. Length 29, height 20, diameter about 7 mm. 

 The beaks are at about the posterior third of the length of the valve. 



Locality. Upper beds, 3373, 3374, 3375. 



This species is abundant but usually more or less distorted by shear- 

 ing. It recalls M. singleyi Harris from the lower Claibornian of Lee 

 County, Texas. 



GASTROPODA 



Drillia ? sp. 



Locality. Upper beds, 3373. 



A much distorted, very imperfect gastropod which may possibly 

 be a Drillia is among the specimens collected. 



