PLATE III. 



Page. 

 SPIRIFERA MAIA 141 



Figs. 1, 1 a. Lateral and dorsal views of young shell, showing area on each valve. Natural 



size. 



1 6. A globose form with a lower area on the ventral valve. Natural size. 

 1 c. A similar form to S. (M.) meristoidcs Meek. 



1 d, 1 e. Ventral and lateral views of a transverse form, with a high area on the ventral 

 valve. (S. 8M&wflifcoa-like.) Natural size. See plate xiv, figs. 13, 13 a. 



C YRTINA DAVIDSONI 146 



Figs. 2, 2 a, 2b. Basal, dorsal, and eide views of a strongly-plicated specimen. Enlarged 



to three diameters. 



2.c, d, e. Views of area, side, and dorsal valve of a smoother shell. Enlarged to three 

 diameters. 



SPIRIFEKA UNDIFERA, var 143 



Figs. 3, 3 a, b. Dorsal, ventral, and side views of the specimen mentioned in the text aa of 

 the type of S. prcematura Hall. Enlarged to two diameters. 



PENTAMERUS COMIS 159 



Fig. 4. Dorsal view of a typical specimen from Independence, Iowa. Natural size. 



7. Same view of a smoother, similar form from Nevada. See plate xv, figs. 5, 5 a, 6. 



SPIRIFERA GLABRA, var. NEVADENSIS 139 



Fig. 5. Dorsal view of a less transverse specimen than that figured on plat* xiv, fig. 14. 



SPIRIFERA UNDIFERA 143 



Figs. 6, 6 a. Dorsal and ventral views of a specimen with closely-arranged cencentric stria? 

 crossing a few low, rounded plications. Natural size. SIM- plate xiv, figs. 11, 

 lla,b. 



MERISTELLA (W.) NASUTA 148 



Figs. 8, 8fl, I. Ventral, dorsal, and side views of a well-marked specimen. Natural size. 



PENTAMERUS Lous 161 



Figs. 9,9 a, &, e. Four views Sf a typical specimen. Enlarged to two diameters. 



