PLATE XXXIII. 



TrACHYPOKA EI.EGANTULA. 

 " Tnicliijiiora eleanntiiln Billings. Cauad. Jourii., New Series, Vol. V, p. 254. May, 1860 



Fig. 1. The upper portion of a small branch, showing the rows of cells. 



Fig. 2. A bifurcating fragment of a larger branch, showing scattered cells. 



Fig. 3. A branch somewhat larger than the ordinary size, sliowing an irregularity in the arrange- 

 ment of the cells. 



Fie. 4. An enlargement of a frajtment, witli very small cells, which have a spiral arrangement. 



Fig. .5. An enlargement from a specimen with large cells arranged in vertical rows. 



Fig. 6. An enlargement of a fragment having large cells with margins unusually prominent and 

 the interspaces strongly striate. 



Fig. 7. Longitudmal section of a specimen, with cells of medium size arranged in vertical rows. 

 "I'liis section shows the cells communicating with a central longitudinal canal, and 

 divided transversely by thickened diaphragms. 



Fig. 8. An enlargement of a fragment with cells of medium size, longitudinally arranged, with 

 finely granulose interspaces. Hamilton group, Darien and other places in Western 

 New York. 



Striatopora (Thajinoptychia) limbata. 



Madrepora limbata Eaton. Geological Text Book, p. 39, pi. 5, fig. 53. 1833. 



Fig. 9. A large ramose fragment, showing the form, mode of growth and distribution of pores. 



Fig. 10. An enlai'gement of the surface, showing the structure between the cells. (The figure 

 does not fully e.\'press the characters.) 



Fig. 11 An enlargement of a bifurcation, showing the distribution of the strite around the mar- 

 gins, but not entering the cells as in ordinary forms of the genus Striatopora. 



Fig. 12. Longitudinal section of a branch, showing the origin and abrupt deflection of the cells 

 toward the external surface. There is no appearance of coutiuuons transverse par- 

 titions, but the inner surface is covered with projecting spinules pointing toward the 

 aperture. 



Fig. 13. Transverse section greatly enlarged, showing the unequal density of the substance between 

 the cells, the spines of the cells, and the cluster of vertical cell-bases in the center 

 before becoming deflected. Hamilton gronp, Darien and westward to Lake Erie. 



The specimen figured by Eaton was from the shore of Lake Erie, at Eighteen-mile 

 creek. 



