256 



NORTH AMERICAN INDEX FOSSILS. 



Lorraine of Ohio, Indiana, Illinois, Missouri, Wisconsin, New 

 Mexico. 



178. H. sinuata Hall. (Fig. 306.) Ordovicic. 



Very similar to H. occidentalis from which it differs in the more 

 elevated and acute beak of the pedicle valve and in the stronger 

 and more regularly bifurcating striae. 



Lorraine of Ohio. 



Fig. 306. Hebertella sinuata. (OhioSurv.) 



x -»-. 





LII. Orthostrophia Hall. 



Pedicle valve depressed convex ; brachial very convex. Surface 

 striated. Cardinal process elongate and simple. Muscular area in 



pedicle valve deep and narrow, 

 almost confined to the space be- 

 tween the dental lamellae. The 

 vascular markings are very distinct 

 on both valves. Siluric-Devonic. 



179. 0.(?) fasciata Hall. (Fig. 

 307.) Siluric. 



Distinguished by its small size, often extended hinge line and 

 bifurcating and fasciculate striae. 

 Niagara of New York. 



FlG. 307. Orthostrophia (?) fasciata 

 (After Hall.) h 



