CORALS AND BRYOZOA. 17 



ten to twelve rows on a branch, separated by prominent serrated ridges, 

 which are frequently wider than the cell apertures, often obscuring them. 

 Twelve serrations in the space of one mm. 



This species is very common, and when well preserved will be easily recog- 

 nized, but when so worn or macerated that the longitudinal ridges are obsolete 

 it closely resembles T. rhombifera. 



Formation and locality. In the shaly limestone of the Lower Helderberg 

 group, near Clarksville, N. Y. 



Trematopora (Obthopora) ovatipora. 



PLATE XI, FIGS 9-11 ; AND PLATE XXIH, FIG. 5 



Trematopora ovatipora. Halt,. Thirty-second Rcpt. N. Y. State Mus. Nat. Hist., p. Lll. 1879. 



.» ■• " Report of State Geologist for 1882. Expl. pi. 11, figs. 9-11. 1883. 



ZoARiOM ramose, solid, very slender; diameter .50 mm. Cell apertures ovate, 

 length .30 mm., width about one-third the length ; disposed in longitudinal 

 parallel rows: margins slightly elevated, and granulose; at the posterior 

  margin of each cell aperture a minute spine ; space between adjacent 

 apertures about .15 mm. Five or six rows on each branch, separated by a 

 slightly elevated granulose ridge. 



This species may be distinguished from T. regularis by its larger, ovate aper- 

 tures and the number of rows on a branch. 



Formation and locality. Lower Helderberg group, near Clarksville, N. Y. 



Trematopora (Obthopora) canaliculata. 



PLATE XI, FIG. 13; akd PLATE XXIII, FIG. 9 



Tranatirpora caruUiculata, Hall. Thirty-secoml Rept. N. Y. State Mus. Nat. Hist., p. 151. 1879. 

 f '• " Repoi-t of State Geologist for 1882. Expl. pi. 11, fig. 1?. 1883. 



ZoABiUM ramose, solid, diameter of branches .90 mm. Cell apertures oval, length 

 .25 mm., width from one-half to two-thirds the length ; disposed in longitudinal 

 parallel rows, alternating : margins distinctly and equally elevated, slightly 

 constricting the opening, sometimes having on one side a minute denticula- 



