PLATE XVI. 

 TROPIDOPORA. 



(Page 553.) 

 Tropidopoea nana, Hall. 

 Fig. 1. A fragment, natural size, with Aulopora. 

 Fig. 2. A portion of the preceding specimen. xl8. 



Upper Helderberg group. Onondaga Valley, JV. Y. 



DIAMESOPORA. 



(Page 566.) 



DiAMESOPOEA CAMERATA, Hall. 



Fig. 3. Several fragments of this species, natural size. 

 Fig. 4. A portion of a branch x6, showing the appearance and arrange- 

 ment of the cell apertures and one of the maculae. 

 Fig. 5. A section showing the cell tubes and epitheca. x6. 

 Upper Helderberg group. Caledonia, N'. Y. 



ACANTHOCLEMA. 



(Page 552). 



AcANTHOCLEMA ALTEENATUM, Hall. 



Fig. 6. A specimen, natural size. 



Fig. 7. A portion of the preceding specimen. x6. 



Upper Helderberg group. Onondaga Valley, JV, Y. 



ACANIHOCLEMA SCDTULATUM, Hall. 



Fig. 9. A portion of a branch. x6. 



Fig. 10. An enlargement showing the usual appearance and arrange- 

 ment of the cell apertures. xl8. 



Fig. 11. An enlargement of a specimen having a pit at the base of 

 each cell aperture in addition to the usual node. 



Fig. 12. A vertical section. xl8. 



Hamilton group. Canandaigua Lake, JV. Y. 



BACTROPORA. 



(Page 553). 



Bacteopora curvata. Hall. 



Fig. 13. A specimen. x6. 



Fig. 14. A portion of the preceding specimen. xl8. 

 Hamilton group. LJrie county, JST. Y. 



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