PLATE 61. 



Pago 

 Figi. 1-8. Geyptoniilla bectieostra 894 



1. Dorsal view ut° a small elougtited specimen. 



2-4. Dorsal, ventral and profile views of a larger and somewhat broader form. 



6. Ventral view of a specimen of large size. 



6-8. Ventral, dorsal and profile views of a broad unsymmetrical form of the ordinary size. 



Fig». 9 - 27. Cetptonella planirostra 895 



9-11. Dorsal, ventral and profile views of a young individual. 

 12, 13. Dorsal and ventral views of a larger specimen. 



14-16. Dorsal, ventral and profile views of a specimen of the ordinary size and form of the 

 species. 



17. Enlargement of the rostral portion of a ventral valve, showing the foramen, deltidial plates 



and teeth. 



18, 19. Dorsal and profile views of a much thickened and gibbous specimen. 



20-22. Dorsal, ventral and profile views of an unusually large specimen, which is much thick- 

 ened, giving gi-eat gibbosity of form. This form is much less common than that of ligs. 

 14-16. 



28, 24. Dorsal and ventral views of a cast of this species, from the Uamiltou group of Hardy 

 county, Va., showing the form of muscular impressions. 



26. An enlarged ventral view of the loop of this species, showing its form and the existence of 

 a band across the dorsal side near tlie base of the crura. 



26. Dorsal view of a very large specimen referred with some doubt to this species. Tlic specimen 

 • in this figure, is represented with the beak broken ofl', I'or the purpose of showing more 



clearly the filling of the rostral parts of the dorsal valve. The muscular impressions 

 and groove left by the slender septum is faintly shown. 



27. Ventral side of the same individual, retaining the beak and showing the muscular impres- 



sions of this valve. 



F^. 28-30. Cryptonella iphis S96 



28-30. Ventral, dorsal and profile views of the specimen described. 



Fi^s. 31-41. Cryptonella (Terebkatula) eudora 398 



31, 32. Dorsal and ventral views of a small, thin specimen of the species 



88. Dorsal view of a small individual, from the Waverly sandstones of Licking Co., Ohio, pre- 

 senting all the specific characters of those from the Chemung group, of New York. 



34, 35. Casts of dorsal valves, showing the muscular impressions. 



36. Dorsal view of a cast, showing the cavities left by the removal of the teeth and dental 

 lamelln. 



87-89. Ventral valves, showing a variety of form and proportions, resulting in some cases from 

 distortion. 



40. Ventral view of a specimen from which the shell is removed in the upper part, and partially 



preserved below. 



41. Ventral view of an individual of the ordinary size, from the Waverly sandstones of Licking 



county. Ohio. 

 (In the progress of this volume it has often been necessary to print the descriptions in advance of 

 making up the plates, and in the present instance the descriptions were printed in ad- 

 vance of the drawings of Tbrebratuda and Cryptonella, and all tlic figures were 

 referred to Plate 61 . In consequence of a greater number of figures tlian antici- 

 pated, it hfts become necessary to designate an additional Plate as 61 a.) 



