PLATE V. 



PlATTCKRAS ECniNATCM. 

 I'agf 13. 

 FIgB. 1, 3. Dorsal Mid lateral views of a small 8|)ecituen, enlarged to twice the natural size, showing the 

 characters of surface when exfuliateii, leaving only the spine-ba^es i-emaining. Fi-om the 

 Hamilton group at Ludlow ville, Cajupi Lake, N. Y. 

 Ffga. 8, 4. Dorsal and lateral views, natural size, of a specimen denuded of the exterior shell and showing 

 the bases uf the spines as tubercles. From the TuUy limestone at Ovid, N. Y. 



Plattc'eras dumosum var. rarispinum. 



P«i'e :«. 



Pig. 5. Latei-al view of a small specimen, showing a few scattered spines. Oneida county, N. Y. 



Figs. 6, 7. Lateral and dorsal views of a largrer ai>ecimen, similar in character to the jireceding. Darien, N. Y. 



Fig. 10. Oblicjue side view of a 8{)ecimen which is partly imbedded in rock, and pi-eserves several of the 



spines in place. Schoharie, N. Y. 



Plattceras formcatum var. contractum. 



Page 12. 

 Figv. 8, 9. Two views of the specimen referred to as a variety in the original description of P. fomicatiua. 



Plattceras dumosum, Conrad. 



Plljre 1*. 



Pig. 11. View of a small specimen preserving several si)inea and spine-bases. Falls of the Ohio. 



Fig. 12. View of a larger and moi-e i-obust sjiecimen, partially imbedded in the rock, and showing numerous 

 spiue-baaes. Schoharie, N. Y. 



Fig. 13. View of a sjiecimen with a large number of broken and displaced spines. From the Comiferous 

 liniestonH near Columbus, Ohio. 



Figs. 14, 1.1. Two views of a large veiitricose individual (the tyjie specimen used by Mr. Conrad for descrip- 

 tion), showing the bases of hollow spines, covering almost the enlii-e surface. Schoharie, N. Y. 



Pig. 16. The ajierture of a long slender specimen, siunlar to tigs. 11 ami 12. The surface shows uumei-ous 

 spine-bases, and a plicated margin. Uelderberg mountains, N. Y. 



