PELECYPODA—PRIONODESMACEA. 519 



ters but differing externally in form and in the strong angular 

 umbonal ridge. Siluric-Carbonic. 



426. G. dubia Hall. (Fig. 697.) Siluric. 

 Small, elongate ; umbonal ridge subangular, a broad shallow 



sinus below it. 



Lower Monroan of Michigan and Ohio. Manlius of New York. 



427. G. perangulata Phillips. (Fig. 698.) Devonic. 



Fig. 698. Goniophora perangulata. (Pal. N. Y., V.) 



Umbo acutely angular. Umbonal ridge elevated, sharp, curv- 

 ing slightly to the posterior basal extremity. Shell beneath the 

 umbo concave. 



New York (Schoharie Grit), Nevada. 



428. G. modiomorphoides Grabau. Devonic. 

 Distinguished from other species by its very short anterior end 



scarcely extending beyond the beaks. 

 • Middle Hamilton (Encrinal limestone) : New York. 



429. G. hamiltonensis Hall. (Fig. 699, c.) Devonic. 

 Length more than twice the height. Margin but slightly curv- 

 ing. Umbonal ridge strongly angular and prominent. 



Hamilton : New York, Pennsylvania. 



430. G. truncata Hall. (Fig. 699, b.) Devonic. 

 Basal margin rounded anteriorly and slightly sinuate near the 



middle. Cardinal line short. Concentric striae on the surface 

 between the umbonal ridge and the sinus crossed by radiating 

 striae. 



Hamilton : New York. 



431. G. ida Hall. (Fig. 699, a.) Devonic. 

 Distinguished by its narrowly elliptical form, the regularly 



curving basal margin ; the hinge line is comparatively shorter 

 than in any other of the Hamilton species except G. truncata. 

 Hamilton : New York. 



432. G. carinata Hall. (Fig. 699, d.) Devonic. 



