EXPLANATIONS OF PLATE 13 (4). 



Obolus conradi. page 368. 



Fig. 1. Yiew of the cast of the dorsal valve, showing the longitudinal septum and the 

 filling of the cavities beneath the margins of the transverse plate. 

 " 2. Cast of a ventral valve showing the impression of the transverse plate, the 

 median depression of the hinge plate and the cavities left by the teeth-like 

 processes. 



Strophodonta profunda. page 369. 



Fig. 3. Impression of the surface of the concave valve of a small individual, with a 

 portion of the filling of the cavity between the valves, showing the impres- 

 sion of the ventral valve on the margin. 



Fig. 4. Impression of the interior of the ventral valve of a large individual. The muscu- 

 lar imprints in the figure are not represented so long as they are in the 

 original specimen. 



Spiripera eudora. * page 370. 



Fig. 5. Dorsal view of a specimen of this species. 

 " 7. Profile view of the same specimen, showing the gibbosity of the valves and 

 the height and curvature of the area. 



Spiripera gibbosa. page 370. 



Fig. 6. View of a dorsal valve of this species. 

 " 8. Cardinal view of a specimen. 



Spiripera plicatella, var, radiata. page 371. 



Fig. 9. Dorsal view of a small individual, showing the extension»of the lamellae in the 

 dorsal valve, as seen in young specimens. 

 '' 10. Ventral view of the same individual, showing the extent of the lamelltein the 



ventral valve. 

 " 11. Profile of the specimen. 



Spiripera meta. page 372. 



Fig. 12. Ventral view of a specimen. 

 " 12. Cardinal view of the same individual, showing the height and exterit of the 

 straight area. 



Spiripera nobilis. page 372, 



Fig. 14. Dorsal view of an individual of medium size. 

 " 15. Ventral view of a specimen showing plications in the mesial sinus. 

 " 16. Ventral view of a large individual. 

 *' 17. Cardinal view of the specimen fig. 16. 



Pentamerus (Pentamerella?) ventricosus. page 374* 



Figs. 18-21. Dorsal, profile, cardinal and front views of a medium-sized individual of 

 the specieS; showing slight indications of plications on the mesial fold and 

 sinus. 



Pentamerus multicostatus. page 373, 



Figs. 22-24. Dorsal, profile and cardinal views of an internal cast of this species, pre- 

 serving the impressions of the costse on the anterior mar^n. 



