American Palaeozoic Bryozoa. 



253 



lime only say, that with but few exceptions their structure is quite 

 different from that of the type species. The same may be said of the 

 majority of the species placed by the same eminent palaeontologist 

 with Trematopora. 



Formation and locality: Niagara Group. The original locality for 

 the species is Lockport, N. Y., but a short time since I collected 

 several examples at Osgood, Ind. 



Callopoka subplana, n. sp. (PI. XI., figs. 7-76.) 



Zoarium ramose, the branches cylindrical, from .2 inch to .5 inch in 

 diameter, and divided dicthoomously at intervals varying from .6 inch 

 to one inch. Cells polygonal in unworn examples, subpolygonal or 

 rounded in worn specimens. The surface exhibits clusters of from 

 four to eight cells, that occasionally are slightly elevated above the 

 general surface, and are conspicuously larger than the ordinary cells 

 which surround them. The latter vary in diameter from -^th to -^-g-tli 

 of an inch (i. e. six to seven cells may be counted in the space of .1 

 inch), while those composing the clusters may attain a diameter of 

 JLth of an inch, though their usual diameter is only about g^th inch. 

 The interstitial cells are comparatively few, being most numerous and 

 noticeable between the large cells of the clusters mentioned. Over the 

 other portions of the surface the}' usuallj- occur at the angles 

 of junction of the ordinary large tubes. They are, however, always 

 inconspicuous, and easily overlooked. 



In longitudinal sections (Plate XL, fig. 7b) the tubes in the axial 

 region of the zoarium, have very thin, flexuous, and often crimped 

 walls. Diaphragms are usuall}' not developed here, excepting a few (six 

 to nine) in the young tubes just above the point of their origin. These 

 are placed at distances apart equaling about two of their diameters at 

 the point of crossing. As the tubes bend outward to reach the surface 

 their walls are thickened, the interstitial tubes make their appearance, 

 and numerous diaphragms are developed in the large tubes, the latter 

 often inosculate, while the distance between them usually varies from 

 one fourth to one half of the diameter of the tube crossed. The dia- 

 phragms in the interstitial tubes are always complete and equally 

 crowded in all. 



Tangential sections (Plate XL, fig. la) show that the tubes just be- 

 low the surface have much thickened walls, their visceral chambers 

 being rounded or oval. The walls of adjoining tubes are seemingly 

 fused together, so that the original boundary line can not be detected. 



