150 KANSAS UNIVERSITY SCIENCE BULLETIN. 



the same locality, but compressed dorso-ventrically, which show the 

 same characters as the type. The size is about that of Aviculopinna 

 americana Meek, but the form and markings as shown on the cast 

 are very different, and the beaks are terminal. Length of type along 

 hinge, 27 mm.; height (20 mm, back of beak), 11 mm. 



Position and locality : Carboniferous, Upper Coal Measures, How- 

 ard limestone, Topeka, Kan. 



The small size, great angle of divergence at the beak and sharp- 

 pointed beaks easily distinguish this species from other' members 

 of the genus from the Coal Measures. 



Pleurophorus whitei, n. ap. Plate V, figs. 5, 56. 



Pleurophorus — ? White, Bull. U. S. Geol. Surv. 77, p. 27, pi. iv, figs. 5-10. 



Shell of medium to large size, transversely ovate, with the depth 

 of the shell greater at the anterior than at the posterior end. Beaks 

 moderately prominent, subterminal ; umbonal ridge prominent, ex- 

 tending obliquely to postero-ventral margin. Hinge straight or arcu- 

 ate, usually about three-fourths the length of the specimen. The 

 right posterior lamina is well shown on good casts. The anterior ad- 

 ductor impression is usually prominent, being set apart by the depres- 

 sion produced by the ridge behind it. The impression of the two 

 cardinal teeth is also visible. The anterior margin drops obliquely 

 downward from the beak nearly to the middle of the shell, when it 

 rounds, rapidly at first, into the ventral margin, which may be straight, 

 somewhat sinuous or even convex on approaching the postero-ventral 

 region : at the end of the umbonal ridge it rounds rapidly into the 

 posterior, oblique truncation, reaching the hinge at an oblique angle. 

 The lines formed by the hinge and ventral margins converge toward 

 the posterior, thus leaving the greatest depth of the shell in front. 

 Above the umbonal ridge the shell is obliquely flattened to the hinge. 

 The surface, as shown in excellent molds, is ornamented only by fine 

 lines of growth, which are sometimes a little stronger beneath the 

 beak than elsewhere, and weaken on and above the umbonal slope. 



Position and locality : This species is found in the Upper Coal 

 Measures, upper Wabaunsee stage, east of Barrett, Kan. This is the 

 only locality known to the writer where this shell, abundant in the 

 Permian, is found below the Wreford limestone. Types from Per- 

 mian west of Stockdale, Kan., "about 100 feet above Cottonwood 

 limestone." Collected by Prof. E. A. Popenoe. 



This species is extremely variable, as shown in Professor White's 

 figures, above cited. The short shell with the posterior shallower 

 than the anterior end is in sharp contrast to most of the species of 

 the genus. In surface ornamentation it resembles P. tropidopJwrus 



