PLATE 54 A. 



Page 



Figs. 1-10. Rhynchonella (Stenocisma) prolipica 343 



1-8. Dorsal views, showing gradation in size nnd form. 



4-6. Veqtral, profile and front views of specimen, fig. 8. 



7. Front view of a small specimen, in which the mesial elevation is not distinctly marked. 



8- 10. Dorsal, ventral and profile views of an unusually large specimen. 



Figs. 11-20. Rhynchonella (Stenocisma) dotis 344 



11-14. Dorsal, ventral, profile and front views of an individual of medium size, having sharply 



angular plications. 

 15-18. Dorsal, ventral, profile and front views of a broad form where the plications are 



rounded. 

 19, 20. Dorsal and front views of a more elongate form, showing a greater mesial elevation. 



Figs. 21-23. Rhynchonella (Stenocisma) carica *. 344 



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



Figs. 24-43. Rhynchonella tenustula , 346 



24, 25. Dorsal and front views of a small ventricose specimen. 



26, 27. Dorsal and front views of a larger but less ventricose, and more finely plicated specimen. 



28, 29. Vontiiil and front views of a specimen not fully grown, showing eight plications in the 



mesial sinus. 

 30-32. Dorsal, ventral and front views of an immature individual, with a slight elevation in 



front and only four plications in the sinus. 

 • 88. Front view of an immature specimen, showing six plications in the sinus. 

 84, 85, 37 - 39. Dorsal, ventral, profile, front and cardinal views of a full grown and gibbous 



specimen, having only five plications in the sinus. The ventral side is denuded of the 



shell and shows the vascular markings. 

 36. Enlargement of the specimen, fig. 35, to show the ramifications of the vascular lines, and 



their origin in the border of the muscular im])ressions. 

 40, 41. Dorsal and front views of an unusually broad individual. 

 42, 48. Front views of specimens which are extremely elevated in this part, with a maximum 



number of plications in the sinus. 



Figs. 44-49. Rhynchonella (Stenocis,ma) coNTRACTA? var. (see addenda). 351 



44-48. Dorsal, ventral, profile, cardinal and front views of a characteristic specimen of this 

 form. 



49. Enlarged ventral view of a smaller specimen, showing a greater number of plications. 



50, 51. Dorsal and ventral views of a specimen, with finer plications, resembling the R. (S.) 



eximia. 



