84 Cincinnati Society of Natural History. 
been excellently described by Dr. Nicholson under the name of Z. 
mammulata. As I have shown in the first part of my memoir, this is 
not the Monticulipora mammulata, of D’Orbigny, but his M. froadosa. 
Heterotrypa subpulchella, Nich., in its typical form, 7. e., flattened 
branches, is a rather rare species at a height of from 300 to 350 feet 
above low water mark in the Ohio river, on the hills surrounding 
Cincinnati, O. This is also about the range of the typical JZ. 
frondosa. Associated with them is a common intermediate form 
having a frondescent zoarium like the last species, from which, on the 
other hand, it differs in having distinct “ macule,” such as charac- 
terize H. subpulchella. Furthermore, in this intermediate form, the 
interstitial cells are not approximately restricted to the “ macule,”’ 
as is the case in H. subpulchella, but a greater or less number are 
distributed indiscriminately over the entire surface. The form under 
consideration clearly demonstrates the close relationship existing be- 
tween H. subpulchella and H. frondosa, bat, as a majority of its 
characters also pertain to the more typical examples of the latter, it 
should be regarded as a variety of that species. The Cincinnati group 
furnishes beside the two species mentioned in the preceding sentence, 
at least four and probably five other forms that are fully as distinct 
from H. frondosa, as is H. subpulchella. These, if I can command 
the space, I propose to describe in the next number of this publication. 
The two species next described (H. vaupeli and H. solitaria) show 
the extremes of the genus so far as observed. The first is a most 
peculiar and beautiful species, and has more interstitial tubes than 
any other species of the genus known tome. Thelatter is characterized 
by the almost total absence of interstitial cells, thus making a near 
approach to Dekayia, Ed. and H. In fact I have found it an exceed- 
ingly difficult matter to draw the line between Heterotrypa and 
Dekayia. Taking the types of the two genera, the differences are of 
course strongly marked. In A. frondosa we have a more or less 
broadly frondescent zoarium, the interstitial cells are quite numerous, 
and the spiniform tubuli are small, and sometimes very numerous, 
In Dekayia aspera, Kd. and H. (the type of the genus), the zoarium 
is irregularly branched, the branches subcylindrical or flattened, 
and the interstitial cells are very few or wanting, while the spiniform 
tubuli are few, but remarkably developed. Compare, however, such a 
species as H. subpulchella with a certain new speices of Dekayia, 
differing in much the same manner from D. aspera, as H. subpuichella 
does from H. frondosa, and the generic differences are not so striking. 
— 
