﻿American Palaeozoic Fossils. 



41 



the Upper Coal Measures. From the Devonian the type species and 

 P. paucirama are described by Hall. A third is described by Rom- 

 inger from the Keokuk Group, under the name of Fistulipora trifolia. 

 The fourth is a characteristic fossil of the Kaskaskia Group, and is 

 next described. While the fifth is known under the name of Ptilo- 

 dictya triangulate, and was described from Coal Measure deposits by 

 White. 



Prismopora serrulata, n. sp. (PI. II., figs. 2, 2a, 26, 2c, 2d, 2e, 2f.) 



Zoarium consisting of remotely bifurcating triangular branches; 

 the sides are sub-equal and slightly concave; the edges sharp, wavy 

 or serrated. Zocecia with small elliptical apertures, separated from 

 each other about twice their diameter; arranged in four or five rather 

 irregular longitudinal rows in the central portion of each face; and in 

 groups of from eight to fifteen cells, often a little larger than the aver- 

 age, and extending to the extremities of the marginal serratures. 

 Between these groups there is a crescentic, smooth, non-celluliferous 

 space. About six cells may be counted in the length of 0.1 inch. 

 In 0.5 inch, from four to six marginal serrations occur. 



In tangential sections (PI. II., fig. 2c) the zocecia are irregularly 

 elliptical in form, with one or two slight inflections of their thin ring- 

 like walls. In the lower levels the vesicular interstitial cells are very 

 distinct; in size they* are very unequal, and in form irregular, while they 

 surround the true zocecia in double or triple series. Just below the 

 surface they are indistinct, and the interstitial spaces appear to be 

 occupied by a dense deposit of sclerenchyma, in the substance of 

 which numerous minute dark dots may be observed, that doubtlessly 

 represent communicating foramina. 



Vertical sections (PI. II., fig. 2e) show that the tubes are at first 

 prostrate, then abruptly bent outward ; in this portion two or three 

 diaphragms cross each tube. The interstitial spaces are occupied by 

 a closely woven vesicular tissue, the meshes of which become obso- 

 lete near the surface. 



In transverse sections (PI. II., fig. 2e) the tripartite character of 

 the zoarium is clearly shown. 



This species is readily distinguished from all other species of the 

 genus known to me by its wavy or serrated margins. 



Formation and locality : Not uncommon in the Kaskaskia Group 

 of the Lower Carboniferous at many localities in Kentucky and Illi- 

 nois. My types are from Tateville and Grayson Springs, Ky. 



