PLATE XVIII. 



ACTINOPTEUIA DECUSSATA. 

 Page lU. 

 See Plates 17, 20 and 84. 

 I'ig-. 1. .\ liiiiri' right valve, preserving' the lamella; of the test. 



Encrinal limestone of the Hamilton g-roup. Eighteen Mile creek, N. Y. 

 Fig. 2. The right valve of a specimen preserving both valves. The left valve is repi-esented in tig. 9. 



Hamilton group. York, Limnystoji Co., N. Y. 

 Fig. 3. A right \alve. The specimen ijreserves several rays on the wing which are not i-epresented in 

 the tigurc. 



Hiunilton group. Geneseo, Livingston Co., N. Y. 

 Fig 4. A .small right valve showing the radii on the wing. 



Hamilton group. Ontario Co., N. Y. 

 Fig. 5. A small left valve. 



Hamilton groui>. Caiiandaigua lake, N. Y. 

 Fig. 6. The left valve of the specimen, fig. 4. 

 Fig. 7. A left valve preserving a portion of the test on the anterior eml. 



Hamilton group. Livingston Co., iV. Y. 

 Fig. 8. A ca.st of a left valve. 



Eucriiial limestone of the Hamilton group. Eighteen Mile creek, N. Y. 

 Fig. 9. The left valve of the specimen tig. 2. 

 Fig. 10. A left valve showing vei-y fine surface radii. 



Hamilton group. York, Livingston Co., N. Y. 

 Fig. 11. A similar specimen of more elongate form. 



Hamilton group. Bellona, Yates Co., N. Y. 

 Fig. 12. A large left valve preserving the greater portion of the test. 



Encrinal limestone of the Hamilton group. Eighteen Mile rreek, Erie Co., iV. Y. 

 Fig. 13. .\ left vahe enlarged to two diameters showing the characters fif surface in a well-preserved 



specimen. 

 Fig. 14. A farther enlargement of the surface, to show the elevated lamellat and the mode of increase of the 



i-adii. 

 Fig. 15. Cardinal view of a specimen jjreserving both valves partly opened. 



Hamilton group. York, Livingston Co., N. Y. 



