182 PALjEONTOLOGY OF NEW YORK. 



This species most nearly resembles T. (O.) regularis of the Lower and 

 Upper Helderberg groups, but the branches are usually more slender, the cell 

 apertures are proportionally larger and more consjjicuous, and there are 

 usually fewer ranges of apertures on a branch : from T. (0.) tortaline.a. it may 

 be distinguished by its more rigid appearance, the more prominent and 

 straighter longitudinal ridges ; when the frond is worn or macerated the 

 longitudinal, parallel arrangement of the cell apertures is preserved, while 

 in that species the obliquely transverse arrangement is the most conspic- 

 uous : from Acanthodema sulcatum, it may be distinguished by the fewer ranges 

 of cell apertures on a branch, by the rounded ridges separating the apertures, 

 and the flattened surface between the ridges: from T. (0.) carinata it may 

 be distinguished by its smaller size, smaller, more distant cell apertures, and 

 the absence of nodes between the apertures : from A. Hamiltonense it is 

 distinguished by its smaller size, fewer ranges of apertures on a branch, 

 and the absence of minute pits between the cell apertures : from T. (0.) 

 bispinulata by its smaller size, fewer ranges of apertures, more prominent, 

 rigid, longitudinal ridges, and the absence of nodes between the cell apertures. 



Formation and locality. Hamilton group, Darien Centre, Erie county, N. Y. 



Trematopora (Orthopora) bispinulata. 



PLATE LV, FIGS. -27-30 ; ANU PLATE J>VI, FIGS. 1«-18. 



CaUopora bUpinulata, Hall. IVans. Albany Institute, vol. x, p. 182. 1881. 



Report of State Geologist for 1883, p. 14. 1884. 



Bryozoum ramose, solid ; bifurcations infrequent ; branches diverging at an 

 angle of forty-five degrees, diameter from 80 to 1.25 mm., enlarging and 

 becoming a little flattened before bifurcation. Cell apertures tubular, arising 

 from the center of the branch, oblique to the axis for about one-half their 

 length, and then abruptly bent toward the surface. Cell apertures oval, 

 length about .25 mm., width from one-third to one-half the length, usually 

 disposed in longitudinal lines, frequently alternating and forming oblique, 

 transverse rows, sometimes somewhat irregularly dispo.sed ; di.stant longi- 

 tudinally the diameter of an aperture. Rows of apertures separated by more 



