﻿28 Cincinnati Society of Natural History, 



large spiniform tubuli, the cavities of which, in several instances, are 

 crossed by faint transverse lines, placed on a level with the successive 

 layers of sclerenchyma before spoken of. When the section passes 

 through the centre of the zoarium, the inferior wall of each tube, just 

 at the base of the " matured " portion, is seen to be angular, and 

 rarely produced into an incomplete diaphragm. As such a section is 

 not readily made, I have figured a portion of one passing a little to one 

 side of the centre. In such sections the angularity of the inferior wall 

 is not noticeable, being obscured by a portion of an adjoining tube. 

 Diaphragms are usually absent, and I have never noticed more than a 

 single one in any tube. 



In the axial region of a transverse section (PI. 1., fig. 16) the cells 

 are polygonal, thin-walled, and increase slightly in diameter out- 

 wardly. In the peripheral region their diameter is somewhat lessened, 

 and their walls much thickened, and traversed by the spiniform 

 tubuli. 



Formation and locality: This is a common species in the Upper 

 Coal Measures of the Western States. The best localities known to 

 me are at Kansas City, Mo., Nebraska City, and Wyoming, in Ne- 

 braska. 



Rhombopora crassa, n. sp. (PI. I., figs. 2, 2a, 26.) 



Zoarium ramose, branches comparatively robust, sub-cylindrical, 

 from 0.10 to 0.18 inch in diameter, dividing dichotomously at inter- 

 vals of 0.75 of an inch, more or less. Zooecia with broadly elliptical 

 apertures, surrounded by a shallow vestibule, and arranged in rather 

 regular obliquely intersecting series, in which six or seven may 

 be counted in the space of 0.1 inch. Margins of vestibules occu- 

 pied by from one to three rows of distinct, subequal granules or 

 spines, which, in the worn state, are represented by an equal number 

 of small pits. Cell walls varying somewhat in thickness with age. 



Tangential sections (PI. 1, fig. 2) show that the zooecial apertures 

 are elliptical, and surrounded, first, by a thin dark ring, in which a 

 large number of excessively minute spots or foramina may be detected; 

 then by a lighter, apparently structureless, band of sclerenchyma, and 

 lastly, by eighteen or twenty rather large and closely arranged spini- 

 form tubuli. The last usually occur in single or double series between 

 the zooecia, but at irregular intervals they are more numerous, and 

 form small " maculae " (see figure). 



In vertical sections (PI. I., fig. 26) the tubes in the axial region of 



