American Palaeozoic Bryozoa, 



165 



tervals of from one fourth to one half an inch. The branches vary in 

 width in different examples, from one to two tenths of an inch. 

 Distance between the first bifurcation and the pointed articulating 

 process, usually less than one half inch. Transverse section of a 

 branch acutely elliptical. Non-poriferous margin broad, distinctly 

 striated. The cells are hexagonal, with circular or oval apertures, 

 and arranged quincuncially ; those near the non-poriferous margin are 

 considerably larger than those along the middle of a branch, where 

 nine or ten occupy the space of .1 inch. 



I know of no species to which P. ramosa is nearly enough allied to 

 necessitate a comparison. 



Formation and locality: Middle Trenton strata, at Lebanon, Tenn., 

 and High Bridge, Ky. 



Ptilodictya briareus, n. sp. (Plate VII., figs. 6, 6a and 6b.) 



Zoarium digitate, from four to six closely approximated and 

 flattened stems arising almost simultaneously from the wedge-shaped, 

 articulating process. As growth proceeds, these stems are dichotom- 

 ously divided at a very small angle, but at rather iregular intervals 

 (Usually about one inch). The non-poriferous margin is wide and 

 striated, the cells are rhomboidal or quadrate, and usually arranged 

 quincuncially. Walls very thick; cell-apertures oval. About seven 

 cells occupy the space of .1 inch, measured longitudinally; in the same 

 space diagonally there are ten. The thickness of the branches varies 

 from .05 inch to .1 inch; the width from .15 inch to .3 inch. The 

 length of the complete zoarium may be three or four inches. 



Formation and locality: The remarkable specimens upon which 

 this species is founded, were collected by Prof. James Safford, from 

 middle Trenton strata at Lebanon, Tenn. 



Graptodictya, nov. gen. 



Zoarium in the general characters like that of Ptilodictya . from 

 which it differs in being smaller, in having subcircular cells, which are 

 surrounded by sulci, or interstitial pits. Non -poriferous margin well 

 developed, striated. Articulating process slender, pointed. Frequently 

 branched above. 



T}^pe, Ptilodictya perelegans, Ulrich. (This Journal, vol. i., p. 94, 

 PI. IV., figs. 16 and 16a.) 



Since the publication of the description of Graptodictya perelegans, 

 I have examined other specimens, which preserve the articulating pro- 

 cess. This is sub-cylindrical and pointed at its lower extremity. 

 About .3 inch above the extremity the first bifurcation takes place. 



