PLA.TE 55. 
Page 
Figs. 1- 8. Rhynchonella (Stenocisma) eximia.. 848 
1. Dorsal view of a small individual of the species, showing no mesial elevation. 
2, 3. Dorsal and ventral views of a larger specimen. 
4-8. Dorsal, ventral, profile, cardinal and front views of a cast. 
Figs. 9-16. Rhynchonella (Stenocisma) stephani. 349 
9. Ventral valve of a young individual. 
10. Ventral view of a cast of a larger specimen. 
11, 12. Profile and front views of the cast of a dorsal valve, having narrow angular plications. 
13-15. Dorsal, cardinal, and profile views of a cast, showing the characters of the dorsal 
portion of the hinge. 
16. Ventral view of a cast, showing the muscular impressions.. 
Figs. 17-25. Rhynchonella (Stenocisma) duplicata. 350 
17-20. Dorsal, ventral, profile and front views of a characteristic specimen of ordinary size. 
21, 22 Casts of dorsal valves, showing muscular impressions, etc. 
23. Cast of a ventral valve, showing muscular impressions. 
24. An enlarged figure of a gutta-percha impression taken from specimen, fig. 22, showing the 
median septum, hinge-plate and crura, and a thickening of the cardinal portion of the 
interior. 
25. An enlarged figure of a gutta-percha impression of specimen, fig. 23, showing muscular 
impression, teeth, etc. 
Figs. 26-39. Rhynchonella (Stenocisma) contracta. 351 
26. Ventral valve of a small specimen with fine plications. 
27. Dorsal valve of a specimen having stronger plications. 
28. Ventral valve of a specimen, showing only two plications in the mesial sinus. 
29-33. Dorsal, ventral, profile, front and cardinal views of a characteristic specimen of the 
prevailing size. 
34, 35. Dorsal and cardinal views of a cast, showing the cavities left by the removal of the 
hinge-plate, teeth, septum, etc. 
36. Ventral valve, showing four plications in the sinus. 
37. Cast of a ventral valve of unusually large size. 
38. Enlarged view of the cast of a ventral valve, showing muscular impression and filling of the 
rostral cavity. From the Hamilton group, four miles south of Cardiff, Onondaga Co., 
N. Y. 
39. Ventral valve of a specimen of this species, from the Waverly sandstones of Ohio. 
Figs. 40-46. Rhynchonella (Stenocisma) orbicularis. 353 
40. Cast of a dorsal valve, showing the triangular filling of the fissure in the hinge-plate. 
41. Cast of a dorsal valve of a broader form, which approaches very closely to R. contracta.' 
42. Cardinal view of the cast of a dorsal valve. 
43. Cardinal view of a cast, showing the cavities left by the removal of the hinge-plate, teeth, etc. 
44. Ventral view of a cast, showing muscular impressions. 
45. Dorsal view of the cast of a large specimen from Chautauque Co., N. Y. The other figures 
of the species are all from specimens collected near Meadville, Pa. 
46. Enlargement from the cast of a ventral valve, showing muscular impressions and dental 
cavities. 
Figs. 47-52. Rhynchonella (Stenocisma) sappho var .. 354 
47. 48. Views of dorsal valves, showing some variation in fo'rm and number of plications. 
49-51. Ventral valves of this species. 
52. Front view of a crushed specimen. 
