PLATE 57. 



Page 

 Figs. 1- 12. Leiorhynchus kelloogi 361 



1-3. Dorsal, ventral and profile views of a small individual. 



4, 5. Dorsal and front views of an attenuated form. 



6. Front view of a gibbous form, contrasting strongly with fig. 5. 



7-11. Dorsal, ventral, profile, front and cardinal views of a full grown and characteristic 



specimen of the species. 

 12. Cardinal viow^ of a cast, showing the cavities left by the removal of the dental lamella:, 



hinge-plate and septum. 



Figs. 13-17. Leioehynchus sinuatus 362 



18. Ventral valve of a small individual. 



14 - 16. Dorsal ventral and front views of a small attenuated individual. 



17. Front view of a more gibbous form. 



Figs, 18 - 25. Leiorhynchus mesacostalis ^ 362 



18. Ventral valve of a small individual. 



19. Ventral view of a larger individual. * 



20. Cardinal view of a large individual. 



21-23. Casts of dorsal valves, showing variations in form, and number of plications in the 

 mesial fold. 



24. Ventral valve of a perfect and characteristic specimen. 



25. Cast of a ventral valve, showing the muscular impression and a narrow mesial sinus. 



Figs. 26 - 29. Leiorhtnohus globdliformis 364 



26 - 29. Views of dorsal valves of this species, showing the rotundity of the shell and the form 

 of the muscular impressions. 



Figs. 30-39. LEPTOCCELIA ACtTTIPLICATA 365 



30, 81. Dorsal and ventral views of a small individual, having a slightly concave dorsal valve. 

 82, 88. Dorsal and ventral views of a specimen of medium size. 



84-87. Dorsal, ventral, profile and front views of a large and characteristic specimen of the 

 species. 



88. Interior of a dorsal valve, showing a slender median septum, cardinal process and dental 



sockets. 



89. Enlargement of the interior of a ventral valve, showing the teeth and muscular impression. 



Figs. 40-45. Camarophoria eucharis 368 



40-44. Dorsal, ventral, cardinal, front and profile views of a characteristic specimen of the 

 species. ' 



46. Ventral view of a specimen, showing the triangular or spoon-sliaped cavity of the ventral 

 valve. 



