262 Cincinnati Society of Natural History. 
tologist, and founder of the genus, Prof. James. Hall, to whom: I am 
indebted for many kindnesses. 
Formation and locality: _ Niagara group, at Waldron, Shelby county, 
Indiana. | ; 
TREMATOPORA WHITFIELDI, n. sp. (Pl. XIII, figs. 4, 4a). 
Zoarium slender, ramose, branches smooth, with an average diameter 
OIL TING) a, and dividing dichotomously at intervals of .4 of an inch, 
more or less. True zocecia subequal, with elliptical apertures, sur- 
rounded by a thin, more or less distinct peristome, and uniformly ar- 
ranged in diagonally intersecting series over the entire surface ; in these 
nine or ten occupy the space of .l inch. The longer diameter of their 
apertures is about ;4,th of an inch. while the shorter or transverse 
diameter averages about ;4,th. The interstitial cells are numerous, 
usually completely isolating the true zocecia. Their apertures vary in 
depth on different specimens, being in some not readily distinguishable 
from the true zoecial orifices, and in others, on account of the inter- 
stitial membrane, scarcely detectable, and only indicated by shallow 
depressions between the peristomes of the true cells, that might be 
overlooked by a careless observer. Well preserved examples show a 
number of small spiniform tubuli, whose position is usually on the 
peristomes. 
Tangential sections show that the true zoccia are elliptical in cross- 
section, that their walls are slightly thickened by a secondary deposit 
on the inside, and that they are almost invariably completely isolated 
by a series of interstitial cells. These are angular, thin-walled, and 
often larger than the true cells. A few spiniform tubuli may be de- 
tected, but not readily, on account of the many particles of pyrites 
of iron, which always obscure, to a greater or less extent, the minute 
internal characters of the bryozoa from the Waldron locality. 
Longitudinal sections show that the true zoccia are entirely without 
diaphragms, and that they are larger and more inclined in the axial 
region, than is the case in 7. halli, approaching in both respects more 
nearly to 7. tuberculosa. The peripheral region is very narrow, and 
near the surface, always one, and often two interstitial tubes separate 
the true zocecia. The interstitial tubes are usually crossed by but 4 
single diaphragm, which is placed about midway between their point 
of origin, and the apertural covering. The tube is generally a little 
constricted where the diaphragm occurs. 
This species differs from 7’. tuberculosa, Hall, in its much smaller. 
