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Cincinnati Society of Natural History. 



ure from those occupying the intervening spaces (e. g., in Prasopora ? 

 cincinnatiensis, James, and Spatiopora montifera, Ulrich). In such 

 species as Monticulipora mammulata, D'Orb. (M. molesta, Nich.) the 

 size of the cells occupying the monticules is about equal to that of the 

 average cells, but their walls are somewhat thicker; while again in 

 other cases (e. g., Monotrypella pulchella, E. and H., Monotrypa undu- 

 lata. Nich., and Discotrypa elegans, Ulrich), the cells which form the 

 monticules are conspicuously larger than the average. The " maculae'' 

 are stellate or irregular spaces constituted by aggregations of inter- 

 stitial cells, which take the place of " monticules." Thej- ma}- be level 

 with the general surface, or slightly* depressed below it (as for example 

 in Amplexopora variabilis, Ulrich, Heterotrypa subpulchella, Nich., 

 and a great number of the species of the F is tulip or idee); or they may 

 be considerably elevated above the general level, as in Atactopora mac- 

 ulata, Ulrich. 



III. Structure of the Walls of the Tubes. — Of much greater con- 

 sequence, from a zoological point of view, than the mere outward form 

 of the zoarium, is the minute structure of the walls of the tubes. This 

 subject has been exhaustively treated by Nicholson in his "Palaeozoic 

 Corals — Monticulipora." and with the exception of a few remarks on 

 the connecting foramina, I can add nothing that he has not already 

 pointed out. Besides, in this writing it is not necessary that I do more 

 than simply mention the principal features of structure. 



(a.) Each tube of the Jlonticuliporidm and Fistuliporidce, whatever 

 its form ma}* be, always possesses a perfectly independent and complete 

 wall. In such species as M. pulchella, E. and H., and M. petasiformis, 

 Nich., this independence of the wall of each individual tube is clearly pre - 

 served throughout the entire growth of the zoarium. In other cases, of 

 which Diplotrypa petropolitana, Pander, Monotrypa undulata, Nich., 

 and 31. briareus, Nich., are examples, this character is not so appar- 

 ent. That the walls are, however, really^ double, is proved beyond a 

 doubt hy the fact that in fractures of the zoarium the tubes always 

 separate cleanly one from another, each carrying with it its own com- 

 plete wall. 



(b.) Connecting Foramina. — Up to the present time I have seen 

 but a single specimen of an undoubted xJonticuliporoid species, w r hich 

 showed in an unmistakable manner that adjacent tubes were brought 

 into connection by minute foramina. The sections showing this char- 

 acter were taken from a good example of 31. obliqua, n. sp. The fora- 

 mina are developed only in the "mature" or cortical region, and the 



