CORALS AND BRYOZOA. 181 



This species most nearly resembles T. (0.) lineata of this geological forma- 

 tion, and T. {().) regularis of the Lower and Upper Helderberg groups ; the 

 diameter of the branches is about the same, but it may be distinguished by the 

 disposition of the cell apertures in sinuous, longitudinal rows ; the ridges 

 separating them are much less prominent than those of the other species ; the 

 whole appearance of the frond is much more irregular : when those species are 

 worn or macerated the longitudinal disposition of the cell apertures remains 

 the most conspicuous. From Acanthoclema sulcatum it is distinguished by the 

 low, rounded ridges, the greater number of rows of apertures, and its more 

 irregular appearance. When worn or macerated it is similar to T. (O.) rhombi- 

 fera of the Lower and Upper Helderberg groups, but the cell apertures are 

 surrounded by low, broad ridges, and not situated in a vestibular area as in 

 that species ; it has also a close resemblance to a macerated condition of 

 Acanthoclema HamUtonense. 



Formation and locality. Hamilton group, Hamburg-on-the-Lake, Erie county, 

 New York. 



Trematopora (Orthopora) lineata, n. sp. 



PLATE LV, FIGS. 3-6; AND PLATE LVI, FIG. 10. 



Zoarium ramose, solid; bifurcations infrequent; branches often diverging at 

 an angle of ninety degrees, diameter about .60 mm. Cells tubular, arising 

 from the center of the branch, oblique to the axis, in contact for about two- 

 thirds their length, abruptly bending outward near the surface. The arrange- 

 ment of the cells is obscurely similar to Acanthoclema. Cell apertures 

 elongate-oval, length .18 mm., width about one-third the length, distant, 

 disposed in longitudinal, parallel rows, eight or nine rows on a branch, 

 apertures longitudinally distant a little more than their length. Peristomes 

 very thin, scarcely elevated. Rows separated by prominent, granulose ridges, 

 which present a minutely serrated appearance, intermediate surface smooth. 

 The granules on the ridges, in the course of growth, form very minute tubuli 

 between the cells. 



