258 Cincinnati Society of Natural History. 
lines of which are, however, often indicated by shallow depressions, 
are covered by a minutely perforated interstitial membrane, which, 
when the zoarium is but slightly abraded, gives the intertubular spaces 
a subsolid appearance. Spiniform tubuli of moderate size are 
devolped more or less numerously. Diaphragms are usually wanting 
in the true zoccia, but in the interstitial tubes a small number is 
always present. Between the diaphragms the tube cavity is always 
more or less inflated, giving this set of tubes a peculiar, but character- 
istic, beaded appearance. in tangential sections, cutting the zoarium 
just below the surface, the proper zocecia are distinguished from the 
angular thin-walled interstitial cells, by their ovate or subcircular form, 
and slightly thicker walls. 
Type, Z. tuberculosa, Hall. 
Of the numerous other forms referred by Prof. Hall to the genus, I 
have examined nearly all of the Niagara group species. Of these I 
find that only three are truly congeneric with the type species. These 
are T. coalescens, TI’. spiculata, and T. solida, the last being still some- 
what in doubt, as my specimens, although from the typical locality, 
and agreeing quite closely with the figures and description of that 
species, are not strictly authentic. I find further, that the common 7. 
ostiolata, Hall, belongs to a new genus of the #stuliporide, which 1 
propose to define and found upon a Lower Carboniferous species in the 
next number of this publication. ‘The internal structure of 7. osculum, 
T. infrequens, and 7. imbricata, from the same formation in Indiana, 
proves these species to belong to my genus Coeloclema of the 
Ceramoporide. Superficially, they greatly resemble 7. ostiolata. 
Of the Lower Helderberg species, I have not yet been able to procure 
specimens, though I expect shortly to receive a lot from Prof. Hall. 
I have, however, before me, some proof copies, kindly given me by that 
eminent authority, of the beautiful plates with which their external 
characters will be illustrated in a forthcoming volume of the New 
York State Survey. Judging from these figures, | am very much 
inclined to doubt that any of them will be found to be correctly referred 
to the genus as restricted and defined by me. Some are doubtlessly 
referable to Meek’s Rhombopora (e. g. T. rhombifera,); others (e.g. 7. 
constricta) I think will be found to possess the characters of Coelo- 
clema, while others again appear to be sufficiently distinet to be regarded 
as belonging to new genera. Of the remaining Upper Silurian, Devo- 
nian and Carboniferous species, I am not prepared to say anything 
inore definite than that, with very few exceptions they will be found to 
differ generically from V7. tuberculosa. 
