518 PROCEEDINGS OF THE ACADEMY OF [Dec, 



In S. sayi Toula the concentric sculpture seems to be decidedly 



closer. 



Thracia (Cyathodonta) gatunensis Toula. PI. XXVI, fig. 3. 



Thracia gatunensis Toula, Jahrb. k.k. Geol. Reichsanst., 190S, LVIII, p. 757; 

 text fig. 1"). 



The shell resembles Cyathodonta spencer i Dall 5 in contour, except 

 that it is apparently not quite so high. The right valve is rather 

 strongly convex, with sculpture of concentric ripples which are as 

 wide as their intervals or slightly wider. The ripples terminate 

 on the rounded ridge which defines the nearly smooth posterior 

 area of the valve. There is a minute irregularly granulose lineo- 

 lation along growth-lines, over the wave sculpture. 



Length 28.5, alt. 21, diam. of right valve about 8 mm. 



Spillway, Gatun Dam. 



While evidently akin to T. spenceri Dall, this species differs by 

 its sculpture, the former having concentric ripples narrower than 

 their intervals. The specimen figured is a right valve, the edge 

 partly imperfect, and the interior concealed by the hard rock. 

 Toula's specimen was larger, 52 mm. long, and the concentric ribs 

 are closer near the beaks. 



Corbula (Cuneocorbula) hexacyma n. sp. PI. XXVI, fig. i. 



Known from the right valve only. The shell resembles C. vimi- 

 nea Guppy externally. The distinctly prosogyrate beaks are at 

 the anterior third of the length, smooth at the tip, posterior end 

 produced, terminating in a short, strongly oblique, straight trunca- 

 tion, the lower point projecting and acute, the basal margin is rather 

 deeply sinuated near the posterior end, elsewhere strongly arcuate. 

 Dorsal margin formed of two straight slopes meeting at an angle of 

 about 130 degrees. The posterior adductor impression rests upon 

 a thick raised ledge which extends obliquely across the posterior 

 end of the interior. There is no lunule. Externally a rather strong 

 keel runs from back to post-basal angle, and an inconspicuous 

 angulation runs to the upper angle of the posterior truncation, 

 defining a lanceolate depressed area. There are irregularly spaced 

 fine growth-wrinkles above the keel. The rest of the valve has a 

 sculpture of very fine, delicate radial threads, and 6 concentric 

 waves, the upper two weak, the others very strong. The region 

 of the beak has no concentric waves. A shell 7 mm. long would 

 show radial striatum only. 



'•> Trans. Wagner Free Institute of Science, III, p. 1527, Oligoceneof Guadaloupe. 



