﻿Cincinnati Society of Natural History. 



The remarkable prominence of the spines of this species will dis- 

 tinguish it from all other species of the genus known. When 

 worn it resembles H. persimilis, with which it is found associated. 

 Its subcircular and larger cell apertures, and thinner interspaces, 

 will, in that case, serve to separate them. 



Formation and locality: Not common in the Kaskaskia Group, at 

 Tateville, Ky. 



Rhombopora wortheni, n. sp. (PI. L, figs. 4, 4a, 46.) 



Zoarium doubtlessly ramose, although all the examples noticed are 

 unbranched, and four of them nearly one inch in length. Stems 

 cylindrical or nearly so, from .05 to .08 of an inch in diameter, and 

 rigid. Zocecia with elongated apertures, narrow vestibule, and com- 

 paratively thin interspaces. Typically their form is oblong quadrate, 

 and their arrangement (as shown in fig. 46, Plate I.) very regular, 

 in vertical and diagonally intersecting lines. Measuring diagonally, 

 eleven cells occupy 0.1 inch, while in the vertical series seven and 

 one half of them occupy the same space. On portions of the surface 

 of other specimens their form is rhomboidal or hexagonal, and the 

 ends of the cells are not truncated, but are angular and wedged in 

 between two alternating cells. A small rounded node or spine, 

 although almost invariably situated between the ends of the cells, is 

 readily overlooked. On account of the extreme brevity of the per- 

 ipheral or " immature ,J region, I have not been able to prepare suc- 

 cessful tangential sections. 



Longitudinal sections (PI. I., fig. 4a) are very characteristic. They 

 show about four extremely long, thin-walled vertical tubes, from the 

 outer ones of which the majority of the tubes opening upon the sur- 

 face are developed by gemmation. In the peripheral or " matured " 

 region of the zoarium, the walls of the tubes have a peculiar form. 

 The basal portion of the "matured" cell is marked by a. spur or in- 

 complete diaphragm, that projects at a right angle from the inferior 

 wall into the visceral cavitjr of the tube. Above this the walls are 

 somewhat thickened and recurved. Diaphragms, other than the in- 

 complete ones described, have not been observed. 



In transverse sections the cells in the central region are usually 

 rhomboidal, nearer the periphery they become hexagonal or poly- 

 gonal. 



While B. wortheni preserves the essential characters of the genus, 

 its internal peculiarities nevertheless separate it widely from all other 

 species known. 



