EXPLANATIONS OF PLATE III. 



PACK 



Fig. 1. a, b, c, d, e,f. . GRYPH^EA CALCEOLA, war. NEBRASCENSIS. . . 74 



1 a. Side view of a young or dwarfed specimen (under valve), showing the incurved beak. 



1 4. Side view of another individual of the same size, with the beak truncated. 



1 c. Under view of the same, showing the longitudinal strize. 



1 d. Longitudinal stria* enlarged. 



1 e,. A larger specimen, with the whole under side of the lower valve occupied by the scar of adhesion. 

 \f. Upper side of an upper valve. 



Fig.. 2. a, b. . . . . PENTACRINITES ASTERISCUS. . . .07 



2 a. One of the segments of the column, natural size. 



2 6. The same enlarged. 



Fig. 3. & 3 b LINQULA BREVIROSTRIS. . . 09 



3. The usual subovate form of the species. 



3 a. A narrower variety. 



Fig. 4 RHYNCIIONELLA ? Dorsal valve. ... .71 



Fig. 5. a, b. . . . . . VOLSELLA PERTENUIS. .... .86 



5 a. Side view. 



6 b. Dorsal view. 



Fig. 6 CAMPTONECTES ? PERTENUIS .78 



The figure represents a cast without the ears, and apparently with only concentric markings. 



Fig. 7. TANCREDIA WARRENANA. .... .90 



Fig. 8 TANCREDIA? ^QUILATERALIS. . . .96 



Fig. 9. a, b, c. . . GRAMMATODON INORNATUS. . . . . . . 90 



9 a. Side view of a somewhat worn or macerated shell. 



9 6. An internal oast showing the impressions of the posterior hinge plates. Those of the anterior 

 side are not represented in the lithograph. 



9 c. An anterior view of one valve, showing its convexity, and the curve of the beak. 



Fig. 10. a, b, c, d, e. . . EUMICROTIS CUKTA . .81 



10 a. Side view of left valve. 



10 6. Radiating striae of same enlarged. 



10 c. Right side of another specimen a little enlarged, showing the deep byssal notch or sinus; 

 also its concentric markings. The latter, however, are too distinct in the lithograph, and 

 curve in such a manner as to indicate that the outline of this valve was subsemicircular 

 when small, while it seems to have been of nearly the same form at all stages of growth. 



10 d. Inner view of a left valve of another specimen ; the hinge margin, however, is broken away. 



10 e. Anterior view of a specimen with the two valves united, though not quite closed below, and a 

 little compressed above. 



Fig. 11. TRIOONIA CONRADI. . . . . . . .83 



Fig. 12. a, b. . . . . ASTARTE ? INORNATA. . ... 94 



12 a. A left valve. 



12 6. Dorsal view of same. 



Fig. 13. a, b, c UNIO'NUCALIS 92 



13 a. Dorsal view. 



13 6. Side view, with anterior margin somewhat broken. 



13 c. Hinge view of an imperfect specimen. The lithograph is not a successful representation of 

 this hinge. It has a small compressed cardinal tooth under the beak, and a long sublaminar 

 posterior lateral tooth, with a furrow above it. for the reception of a similar tooth in the 

 other valve. 





