BRACHIOPODA — ORTHIDJE. 263 



B. Pointed posteriorly, ;'. e. , with somewhat elevated beak **. 



** Small (width not exceeding % inch) 3. 



3. With slight mesial depression. Beak not incurved 194. R. hybriaa. 



3. With strong mesial sinus. Beak of pedicle valve somewhat incurved. 



204. R. ditbia. 

 ** Of medium size (not below | inch in width) 4, 



4. Curved posteriorly. 199. R. leucosia. 



4. Straight posteriorly 203. R. burlingtonensis. 



194. R. hybrida (Sowerby). (Fig. ^^^^t *\ 



3 1 5.) siiuric. m H ^p » m 



Width exceeding length. Valves ^HSP^ 



very nearly equal. Beaks scarcely ^^ 



incurved. Pedicle valve marked with /"*' < , r 



a broad, undefined depression. I I I j 



Niagaran of New York, Kentucky, ^Hi^ ^H 



Tennessee, Ohio, Indiana, Missouri, FlGm 3l$ . Rhipidomella hybrida. 



Nova Scotia. (After Hall.) 



195. R. oblata Hall. (Fig. 3 16-3 17.) Devonic. 



Large, transversely oval. Pedicle valve convex at beak and 



concave toward the front. Brachial valve very convex. Beaks of 



/> 



Fig. 316. Rhipidomella oblata. (After Hall.) 



FlG. 317. Rhipidomella oblata internal molds. (After Hall.) 



