PLATE 101 A. 



Pnge 



Fig. 1 a - h. Eatonia peculiaris. 436 



1 a. Interior of the ventral valve, showing the form of the muscular impressions, teeth, etc. 



1 6. Profile of the same, showing the little elevations of the shell -surface, and the small pits . 

 for the adductor muscles a and the teeth t. 



1 c. The dorsal valve, showing the crural processes and muscular impression. 



1 d. Front view of the same, showing the deep sinus, and the relation of the crural processes 



and median septum. 

 1 e. Section of the dorsal valve, showing the elevation of the median septum and the crnral 



processes. 



1 /. Figure of the ventral valve (the inflected extension in front being removed ) with a part 

 of the dorsal valve attached, showing the crural processes, the median septum of the 

 dorsal valve, the adductor imprints, the small oblique pits penetrating beneath the 

 lamina! of the shell, and the cardinal muscular impression. 



] g. View of another specimen with the dorsal valve downwards-and the ventral valve broken 

 away, to show the median septum articulating with the bifurcating cardinal process of 

 the dorsal valve. 



1 A. A cast of the ventral valve, showing the muscular and vascular impressions. This and 

 the preceding figure are enlarged to once and a half the natural size. 



Fig. 2 a, b. Eatonia wiiitfieldi. 437 



2 a. The exterior of the ventral valve. 



2 6. The interior of the ventral valve, with the apex of the dorsal valve attached. 



Fig. 3-6. Eatonia sinuata. 438 



3 a. Dorsal view of a large individual, which shows the prevailing form. 



3 6, e. Profile and front views of the same. 



4. Dorsal view of a more orbicular form. 



6. Ventral view of a cast, showing the strong muscular impression with the small central 

 adductor impression. 



6. Ventral view of a cast preserving a part of the shell; the form of the shell and mnscular 

 impression more rotund than the preceding. 



Fig. 7 & 8. Rhynchonella ramsayi. 446 



7. View of the dorsal side of the specimen. 

 8 a, b. Ventral and dorsal views of the cist of this spec'oi. 



