Pe AMISH leks 
Disciya NEWBFERRYI 
Fig. 1. Lateral view of the specimen figured on plate xviii, fig. 3. 
ERODUCEUS SUBACUDEAINUS-seeerieces=n= cea eitee eee ea sete eee eee eae cee eee ene eee aee 
Fig. 2. Ventral valve. Natural size. See plate xiii, figs. 19, 20. 
DISCINA CONNATA 
Fig.3. Ventral valve. Natural size. 
3a. Side view of fig. 3. 
DISCINA NITIDA 
Figs. 4, 4a. Interior of compressed ventral valves, showing the smooth inner surface and 
rougher outer surface marked by strong concentric striz. 
RETZIA RADIALIS 
(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, Retzia Verneuiliana Hall, a specimen from the Lower Carboniferous of the Little 
Belt Mountains, near Clendenin, Montana. 
5b. From the Devonian White Pine shale. 
5, d,e. Lower Carboniferous forms from the Eureka District. 
5f, g, h. Upper Carboniferons forms from the Eureka District. 
RHYNCHONELLA THERA 
Figs. 6, 6 a, b, ec. Dorsal, lateral, and ventral views of a typical specimen, enlarged to two 
diameters. 
TEREBRATULA HASTATA 
Figs. 7,7 a. Dorsal and ventral views of a somewhat crushed specimen. Natural size. 
7b. Lateral view of a more perfect shell. Natural size. 
SPIRIPERAUDESIDERATA: SoS ae Santee croc cece sein oe eee or ce See SE ee ee 
Fig. 8. Dorsal valve. Natural size. 
214 
213 
220 
223 
224 
217 
