348 



NORTH AMERICAN INDEX FOSSILS. 



400. W. ? nucleolata (Hall). (Fig. 449.) Siluric. 

 Beak of pedicle valve pointed and incurved. Front of shell 



indented. Surface with concentric growth lines. This species is 

 less elongate than IV. nitida and the frontal indentation is more 

 conspicuous. 



Cobleskill of New York, Wisconsin. 



401. W. sulcata (Vanuxem). (Fig. 450.) Siluric. 

 Distinguished by its elongate form, strongly ventricose character 



and well marked mesial sinus in the pedicle valve. 

 Cobleskill and Manlius of New York. 



a 





' 3> 



Fin. 449 Whitfield- Fig. 450. Whitfieldella Fig. 451. Hyattella con- 

 ella nucleolata (Pal. N. sulcata. (After Grabau. ) qesta (Pal.N. Y., II.). 



V., II.). 



CXVI. Hyattella Hall and Clarke. 



Small, nearly five-sided. Valves subequally convex. Differs 

 from Whitfieldella in the form and in the absence of a median 

 septum in the brachial valve. Siluric. 



^ 



b 



>^ ■ 2 



Fig. 452. Hyattella congesta (Pal. N. Y., II.). 



402. H. congesta (Conrad). (Figs. 45 1-452.) Siluric. 



Gibbous. Pedicle valve strongly convex with a deep median 

 furrow which deepens and widens toward the front. Strong fold 

 on brachial valve with a more or less prominent lateral fold on 

 each side. 



Clinton of New York, Pennsylvania, Ohio, Kentucky. Ontario. 



