252 Cincinnati Society of Natural History. 
the true cells is experienced. This is mainly due to two reasons. 
First, the cystoid diaphragms, a series of which is apparently developed 
in each of the proper zocecial tubes, are always attached to the concave 
side of the tube, and unless the section passes along the direction of 
growth, these diaphragms present the same appearance that those of 
the ordinary straight kind do. Secondly, we find that the horizontal 
diaphragms of the interstitial tubes, are but little, if at all, more na- 
merous than the cystoid diaphragms of the true zoccia. There is one 
feature, however, by means of which I believe the two sets of tubes 
may be at all times distinguished: namely, the interstitial tubes are 
crossed by diaphragms at regular intervals throughout their length, 
while the true cells, near their apertures, are always filled by the sur- 
rounding matrix. The spiniform tubuli are very conspicuous in these 
sections, and nearly always show the central lucid line, which in several 
instances appears to be crossed by numerous horizontal partitions. 
This species differs from all the others of the genus known to me, 
in the size and prominence of the spiniform tubuli. Compared more 
critically with A. mundula (Pl. XIL., figs. 6 and 6a), we find the follow- 
ing differences. In that species the spiniform tubuli are considerably 
smaller, and less prominent, the intertubular spaces narrower, and, in 
consequence, the interstitial cells smaller, and less numerous, while the 
diaphragms in the interstitial tubes are about twice as numerous in a 
given space, 
Named in honor of my esteemed friend, Mr. Charles Suimonee who 
kindly gave me, among other interesting forms, a large and most bean- 
tifully preserved example of this species. 
Formation and locality: Examples of this species are rather rare in 
the upper beds of the Cincinnati group, but occur perhaps at most the 
localities exposing these layers. The best specimens, however, were 
obtained from near Oxford, O. } 
ATACTOPORELLA MUNDULA. Ulrich (Pl. XIL., figs, 6, 6a). 
Atactopora mundula, (Ulrich, Jour. Cin. Soc. Nat. Hist , vol. ii., p. 123, Pl. XI1_., figs. 4; 
4a, Oct. 1879. 
Zoarium attached to foreign objects, such as Heterotrypa frondosa, 
D’Orb., and Ptilodictya pavonia, D’Orb., forming irregularly outlined 
expansions, usually less than one inch in diameter, that, only when the 
colony consists of more than one layer, have a thickness exceeding .04 
ofan inch. Surface exhibiting at rather regular intervals of about .1 
inch, more or less prominent monticules, on which both the cells and 
