146 Cincinnati Society of Natural History, 



t 



(3) . As regards the structure of the wall, we know of at least one 

 species of Monticulipora, the M. (Trematopora) obliqua, n. sp., in 

 which the walls of the tubes, in the peripheral portion of their course, 

 are pierced by connecting foramina. On the other hand, there are a 

 number of species of Heteropora in which no traces of these foramina 

 have yet been clearly proved to exist. In all other respects the minute 

 structure of the walls appears to be the same in both. 



(4) . Nothing of the nature of radiating "septa" are known to exist 

 in any Monticuliporoid species. In Heteropora neozelanica, Busk, 

 Dr. Nicholson has shown that the tubes in the peripheral part of their 

 course are intersected by numerous delicate spinules, which are 

 arranged in a radiating manner, and extend sometimes nearly to the 

 center of the tube-cavity. He says of this feature: "These spinules 

 in form and arrangement precisely resemble the "septal spines" of 

 many species of Favosites; but admitting the Polyzoan affinities of 

 Heteropora, it is obvious that they can not be compared homologically 

 with the septa of any Coelenterate." So far as my observations have 

 extended, I have never seen any species of Favosites in which the 

 "septal spines" were nearly so slender as the spinules figured by Dr. 

 Nicholson in the tubes of H. neozelanica. As a solution of these 

 remarkable structures, I would suggest that they may have originally 

 constituted calcareous ribs in diaphragms that otherwise were con- 

 structed of a material which during maceration was destroyed. 



(5.) " Spiniform tubuli" are developed in a majority of the Monticu- 

 Hporido}, and the appearance presented by similar structures in 

 tangential sections of Heteropora conifera, is precisely like that seen 

 in a like section of Leioclema punctatum. These structures are also 

 present in Heteropora attenuata. 



(6.) Lastly, we will weigh the points of resemblance and difference. 

 On the one hand we have a strong external resemblance, a general 

 similarity in the construction of the zoarium, and an agreement in the 

 facts, that in both — (1) the colony is composed of two sets of tubes; 

 (2) both have their tubes crossed by diaphragms; (3) in such types 

 of the Monticuliporidce, as Leioclema punctatum, and Callopora (?) 

 cincinnatiensis, the interstitial tubes are in no other way structurally 

 different from the proper zooecia, than in being crossed by more 

 numerous diaphragms. Again, while no traces of connecting foramina 

 have yet been detected in several species of Heteropora, such foramina 

 are now known to exist in at least one undoubted Monticuliporoid 

 species. 



