A ID 
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274. Cincinnati Society of Natural History. 
zocecia show a central, obscurely circumscribed area, that may repre- 
sent the openings of opercula of previous layers. These sections show 
further, that whenever the horizontal partitions are brought to light, a 
large number of concentrically arranged, dark or lucid spots may be 
detected, which in the true cells gradually increase in size toward the 
circumference. a ‘ . 
Vertical sections (Pl. XIIL., fig. 1b) show that the tubes arise rather 
abruptly from the attached basal membrane, near which their walls are 
comparatively thin. The upward direction of the tubes is often so ir- 
regular that a section can not be made to pass through their full length. 
The most regular portion seen in any of my sections is represented by 
the figure above referred to. From this section we learn, first, that 
both the vertical and horizontal partitions are of variable thickness 
(the extremes are shown in the figure); secondly, that the latter are 
developed at approximately the same level, and at nearly equal and 
short intervals, in all the tubes; thirdly, that there are no certain 
marks by means of which one set of cells may be distinguished from 
the other; and lastly, that a row of dark spots may often be detected 
in the lower half of the thick horizontal partitions. 
I have not now the time, nor am I perhaps fully prepared, to discuss 
the affinities of this remarkable form. It presents characters that are 
at total variance with the Monticuliporide, and nearly all other 
bryozoa known tome. My opinion of Jdiotrypa is, that its zoarium 
consists of more or less numerous layers of cells, which, just as is the 
case in some of the Celleporide (e. g. Cumulipora, Mstr. emend. 
Reuss.), being developed one from the other, in direct sequence, 
eventually assume a tubular character. Further, I believe, that the 
horizontal partitions represent the opercula of previous layers which 
were left behind at successive stages in the growth of the zoarium. 
These opercular coverings were, I am convinced by the evidences at 
hand, perforated by minute foramina, which in their subsequent use 
as the floor of the succeeding layer of cells, have been filled up, and the 
whole generally thickened by a secondary deposit of sclerenchyma. In 
the course of this memoir, I have several times stated that a similar 
method of reproduction, at least in the “ matured’ or peripheral 
region of the zoarium, is indicated in several members of the MMoniv- 
culiporide (e. g. Callopora, Hall, and Stenopora, Lonsdale). Between 
Tdiotrypa parasitica, and those forms, there is, however, this funda- 
mental difference, that in the new genus the zoarium is not divided 
