PLATE VII. 



Page. 

 DISCINA NEWBERRYI 213 



Fig. 1 . Lateral view of the specimen figured on plate xviii, fig. 3. 



PRODUCTCS SUBACULEATUS 214 



Fig. 2. Ventral valve. Natural size. See plate xiii, figs. 19, 20. 



DISCINA CONXATA 214 



Fig. 3. Ventral valve. Natural size. 

 3 a. Side view of fig. 3. 



DISCINA NITIDA 213 



Figs. 4, 4 a. Interior of compressed ventral valves, showing the smooth inner surface and 

 rougher outer surface marked by strong concentric strise. 



RETZIA RADIALIS 220 



(A series to illustrate the variation in the number and size of the radiating surface plica- 

 tions, all enlarged to two diameters.) 

 Figs. 5, 5 a, Eetzia Virneuiliana Hall, a specimen from the Lower Carboniferoas of the Little 



Belt Mountains, near Clemlenin, Montana. 

 5 6. From the Devonian White Pine shale. 

 5 c, d, e. Lower Carboniferous forms from the Eureka District. 

 5/> 9) ^ Upper Carboniferous forms from the Eureka District. 



RHYNCHONELLA THKRA 223 



Figs. 6, 6 a, b, c. Dorsal, lateral, and ventral views of a typical specimen, enlarged to two 

 diameters. 



TEREBRATULA HASTATA 224 



Figs. 7, 7 a. Dorsal and ventral views of a somewhat crushed specimen. Natural size. 

 7 6. Lateral view of a more perfect shell. Natural size. 



SPIRIFERA DESIDERATA 217 



Fig. 8. Dorsal valve. Natural size. 



