2^2 



NORTH AMERICAN INDEX FOSSILS. 



Trenton of New York, Pennsylvania, Wisconsin, Minnesota, 

 Ontario, Manitoba. 



LXIV. Anastrophia Hall. 

 Differs externally from Parastrophia in having a more prominent 

 umbo in the brachial valve and in that the valves are covered with 

 many sharp plications extending to the beaks. Siluric-Devonic. 



Fig. 327. Parastrophia hemiplicata (Cana- 

 dian Geol. Surv. ). 



Fig. 328. Anastrophia interplicata 

 (N. Y. State Surv.). 



220. A. interplicata Hall. (Fig. 328.) Siluric. 

 Subovate. Brachial valve much more convex than the pedicle. 



Beaks very short and closely incurved. Plications three or four on 

 each side of the beak near the cardinal margins; an additional one 

 is inserted between each pair, except the central ones, about half 

 way toward the front. 



Niagaran of New York, Kentucky and Wisconsin. 



221. A. internascens Hall. (Fig. 329.) Siluric. 

 Ovoid or subglobose with brachial valve slightly the more 



gibbous. Pedicle valve with depressed anterior portion marked by 



Fig. 329. Anastrophia internascens. 

 (After Hall.) 



Fig. 330. Anastrophia verneuili (Cana- 

 dian Geol. Surv.). 



a broad, undefined sinus and short beak closely incurved over 

 umbo of opposite valve. Brachial valve elevated in center, some- 

 times forming a broad undefined fold. 



Niagaran of Kentucky, Indiana, Wisconsin. 



