EXPLANATION OF PLATE X. 



{Figures all of natural size.) 



Cyrtina '.' Curupira, Rathhun, sp. nov., page 243. 



1 and 6. Doi'sal valves. 

 Betzia Wardiana, Hartt, sp. nov., page 245. 



3, 4, 5, 8, 11, 12 and 14. Ventral valves. 



16. Ventral valve, with the plications finer and more numerous than in the 

 majority of specimens. 



3 and 9. Dorsal valves. 



Orthis Nettoana, Rathhun, sp. nov., page 347. 

 7 and 13. Ventral valves. 

 10. Dorsal valve. 



Terel)ratula Derbyaiia, Hartt, sp. nov., page 330. 

 15, 18, 34 and 35. Ventral valves. 



17, 19, 31 and 33. Dorsal view of specimens of which both valves are 



preserved. The beaks of the ventral valves are seen extending 

 beyond the dorsal valves, but in all the specimens they are more or 

 less defective. 

 20. Dorsal valve. 



Tropidoleptus carinatus, Con., (sp.,) page 354. 



26. Exterior mould of dorsal valve, very much broken. 



Retzia Jamesiaiia, Hartt, sp. nov., page 343. 



39, 33, 34, 36, 37 and 38. Ventral valves, showing the enlarged median 

 depression. 



37, 38, 31, 33 and 35. Dorsal valves. 



30. View of dorsal valve of a specimen in which both valves are pre- 

 served. The beak of ventral valve is slightly extended beyond the 

 dorsal valve. 



23. Dorsal view of a rather narrow specimen, of which the ventral valve 

 is also preserved. The plications are less in number than usual. 



Chouetes Herbert-Smitliii, Hartt, sp. nov., page 351. 



39, 41, 43 and 46. Ventral valves of ordinary size. 



44. Ventral valve, same as above, but smooth from the character of the 

 rock in which it occurred. 



40. Ventral valve, rather above the average size. 

 45 and 47. Exterior moulds of dorsal valves. 



Clioiietes Onettiana, Rathhun, sp. nov., page 353. 



43 and 48. Ventral valves, with nearly smooth surfaces and showing the 

 short median septum very distinctly. 



(Except where otherwise stated, the above specimens are all of interior 

 moulds.) 



