PLATE 54. 



Page 

 Figs. 1-8. Rhtnchonklla (Stenocisma) tethts 385 



1 -8. Dorsal, yentral and profile views of a small specimen of the species. 



4-8. Dorsal, ventral, profile, cardinal and front views of a large individual of the species. 



Figs. 9-13. Rhtncuonella (Stenocisma) billinobi 336 



9. An enlarged dorsal view of a yovmg individual, specimen, fig. 11. 

 10. Enlarged dorsal view of another 8i)ecimen. 

 11-13. Ventral, profile and fVont views of a specimen of this species. 



Figs. 14-19. Rhynchonella (Stenocisma) Carolina 337 



14 - 18. Dorsal, ventral, profile, cardinal and front views of a cast, showing the general features 

 of the spc ies. 



19. Front view of a less gibbous specimen. 



Figs. 20-23. Rhynchonella (Stenocisma) royana 338 



20-23. Dorsal, ventral, profile and front views of the specimen described. 



Figs. 24-32. Rynchonella (Stenocisma) horskordi 339 



24. Dorsal view of a specimen of medium size, which is somewhat thickened on the margin. 



20. Front view of a smaller individual. 



26, 27. Dorsal .lud profile views of a more globose spucimen. 



28-32. Dorsal, ventral, profile, cardinal and front views of a large, well formed, and charac- 

 teristic specimen of .the species. 



Figs. 33-43. Rhynchonella (Stenocisma) sappho 340 



33. Ventral valve of a specimen, referred with some doubt to this species, ^'rom the Upper 



Heiderbcrg limestones. 

 84, 35. Dorsal and ventral views of a medium sized individual of the species. 

 86. 37. Dorsal views of two individuals of a larger size, showing .some variation in the general 



outline of the shell 

 88-42. Dorsal, ventral, profile, cardinal and front views of a large and characteristic specimen 



of the species. 

 48. Front view of a still larger individual, showing a greater gibbosity. 



Fig8.44-59. Rhynchonella (Stenocisma) conoreoata 341 



44, 45. Dorsal and front views of a small globose fomi of the species. 



46-60. Dorsal, ventral, profile, cardinal and front views of a full grown and characteristic 



specimen. 

 51, 52. Ventral views of casts of the species, showing considerable variation in the form of the 



muscular impressions. 

 68, 54. Ventral and cardinal views of a more elongated form, showing the cavities left by the 



removal of the dental lamellte and hiiige-plato; also the median septum and the filling of 



the small triangular fissure in the beak of the dorsal valve. 



65. Dor»il view of a cast of this species. 



66, 57. Enlargements of the cardinal parts of the casts of dorsal valves, showing the filling 



of the rostral cavities and fissure. 

 68, 59. Enlarged views of artificial casts made in the natural moulds of the dorsal valves, show- 

 ing the hinge-plate, dental sockets, median septum and triangular fissures in different 

 stages of development. 



