NEW YORK STATE MUSEUM 



slightly anterior. On the left valve the prodissoconch is generally con- 

 spicuous in adult stages. Hinge line short, straight, extending backward 

 for a little distance, then deflected downward, the posterior margin having 

 a slight outward curve. At the posteroventral angle it is more or less 

 abruptly deflected to the transverse basal margin, which at the anteroven- 

 tral angle is bent upward in a more or less abrupt curve, which gradually 

 recurves to the beak. The subangular umbonal ridge is well marked on 

 the posterior moiety of the valve, reaching the margin at the posteroventral 

 angle, and along this ridge all the folds of the surface are quite abruptly 

 bent. The posterior slope is moderately broad and clearly defined. Sur- 

 face gently and pretty regularly convex ; marked by very coarse concentric 

 corrugations, generally five to six in number, separated by narrow grooves. 

 The right valve is very seldom seen ; that referred to the species is 

 obliquely subovate, with subanterior beaks ; basal margin rising rather 

 abruptly to the anterior extremity, while the posterior margin is broad and 

 a regular curve. The vertical diameter of the valve across the posterior 

 portion is nearly twice that through the umbo. From the beak obliquely 

 backward extends a depression increasing in width downward, which 

 divides the surface into a narrow anterior and broad posterior convexity. 

 The latter is again depressed and flattened toward the hinge line. Sur- 

 face with concentric wrinkles, which may be covered by finer concentric 

 lines. 



Habitat. Genesee province ; Chautauqua subprovince. Walnut creek 

 at Forestville and Correll's point on the Lake Erie shore near Brocton. 



Observations. Loxopteria corrugata is a species closely 

 similar to Kochia (L. ) rugosa Freeh, which has been described from 

 a single left valve from the Upper Devonic at Beilstein near Oberscheld. 1 

 This attains a larger size than we have observed in the New York speci- 

 mens, and we note that there is an apparent difference in the development 

 of the umbonal ridge. L. rugosa is represented as having an elevated, 

 somewhat incurved postumbonal slope, free of corrugations, but in the 



*Op. cit. p. 78, pi. 6, fig. 5, 5a. 



