I 



PLATE VII. 

 Triplegia Niagarensis, Hall. 

 Page 351. 

 Figs. 1, 2, 3, 4. Cardinal, oblique cardinal, anterior and profile views of an 

 internal cast, showing the sharply defined median fold and sinus on 

 brachial and pedicle- valves, respectively, the marginal plication and the 

 cavity left by the cardinal process. 

 Niagara dolomites . Near Milwaukee, Wisconsin. 



Stbophalosia cymbula, Hall. 

 Page 355. 

 Fig. 5. The exterior of a pedicle-valve, showing the scar of attachment. 

 Keokuk group. Lebanon, Kentucky. 



Stbophalosia Rockfordensis, Hall. 



Page 358. 



Figs. 6, 7, 8. Dorsal, cardinal and ventral views of a specimen, showing the 

 external characters and size of cicatrix . 

 Upper Devonian. Eockford, Iowa. 



Figs. 9, 10. Cardinal and dorsal views of a larger, but incomplete example . 

 Upper Devonian. Eockford, Iowa. i 



CflONOsTROPHiA Helderbergia, Hall. 



Page 353. 



Fig. 11. A specimen in which the valves are opened, exposing their internal 

 surface, showing the extremely fine radial striation, teeth and cardinal 

 process. 

 Lower Helderberg group. Near Clarksville, N. Y. 



SpIRIFEE crisp ATU8, Hall. 



Page 355. 



Figs. 12, 13. Views of the original specimen, showing the coarsely jUicate 

 surface. 

 Niagara group. Maryland. 



Spirifer Canai^daigu^, Hall. 



Page 355. 



Figs. 14, 15. Ventral and profile views of a somewhat imperfect individual, 

 showing the low rounded lateral plications . 



Fig. 16. Enlargement of the surface, showing the closely crowded concentric 

 row of fine granules or spine-bases. x5. 

 Hamilton group. Canandaigua Lake, N. Y. 



386 



