CORALS AND BRYOZOA. 71 



This species closely resembles T. (0.) rhombifera, but the apertures are com- 

 paratively larger, more closely disposed, and the branches have a more delicate 

 appearance. 



Formation and localities. Upper Helderberg group, near Waterville, and 

 Onondaga valley, N. Y. 



Trematopora (Orthopora) regularis. 



PLATE XXV, FIGS. 27, 28 ; AND PLATE XXVI, FIGS. 5, 6. 



Trematoyora regularis. Hall. Twenty-sixth Kept. N. Y. State Mus. Nat. Hist., p. 105. 1874. 

 Orthopora " " Report of State Geologist for 1885, advance sheets. Expl. pi. 2.5, figs. 27, 



28. 1886. 



The specimens from the Upper Helderberg group, referred to this species, 

 present essentially the same characters as those of the Lower Helderberg group, 

 described on page 16. 



Formation and locality. Upper Helderberg group. Falls of the Ohio river. 



Trematopora (Orthopora) rhombifera. 



PLATE XXV, FIG. 29 ; AND PLATE XXVI, FIGS. 3, 4. 



Treutatopora rhomhlfera. Hall. Twenty-sixth Rept. N. Y. State Mus. Nat. Hist., p. 106. 1874. 

 Orthopora " " Report of State Geologist for 1885, advance sheets. Expl. pi. 25, fig. 29. 



1886. 



The specimens from this horizon present essentially the same characters as 

 the forms of the Lower Helderberg group, described on page 18. 



Formation and locality. Upper Helderberg group. Falls of the Ohio river. 



TROPIDOPORA, Hall. 1886. 

 Tropidopora nana. 



plate XXV, FIGS. 25, 26. 



Tropidopora nana. Hall. Report of Stale Geologist for 188.i, advance sheets. Expl. pi. 25, figs. 25, 26. 



1886. 



ZoARiUM ramose, solid; branches .60 mm. in diameter Cell apertures broadly 

 oval or circular, diameter .16 mm.; disposed in irregular longitudinal 

 rows, which are separated by sinuous ridges : peristomes very thin, slightly 

 elevated. 



