2 90 TABULATE CORALS. 



undoubted corals as Favosites among the Zoantharia, and 

 Heliolites among the Alcyonaria. Again, there is the import- 

 ant character that the corallum of the MonticuHporoids can be 

 shown to be almost always (I expect, always) dimorphic, con- 

 sisting of two distinct sets of corallites, of different sizes, and 

 mostly with a different internal structure. This last character 

 reminds us so strongly of the Helioporidce — to which there 

 are other mentionable points of likeness — that I am at present 

 disposed to regard the MotiticuliporidcB as an ancient group 

 of the Alcyonaria. 



As for the relations of MonticuUpora to other types of the 

 so-called " Tabulate Corals," the genus is separated from all 

 the Favositida;, including the similar-looking Stenopora, Lonsd., 

 by the possession of imperforate walls to the corallites.^ Ad- 

 mitting the absence of mural pores, in the want of direct evi- 

 dence to the contrary, we have only to compare MonticuUpora 

 with a very limited number of types, of which the most im- 

 portant is Chcstetes of Fischer. From this latter the present 

 genus is sufficiently distinguished by the non-amalgamation of 

 the walls of contiguous corallites, by the want of the curious 

 vertical ridge which is found in the interior of many of the 

 corallites of Chcstetes, and by the possession of two sets of 

 corallites in the corallum, one set of tubes being commonly 

 disposed in special groups. From Tetradium, Dana, Monti- 

 ctilipora is sufficiently distinguished by its total want of septa 

 and by the dimorphic structure of the corallum. To Heliolites 

 and its allies the various types included under the general 

 name of MonticuUpora present a considerable alliance, especi- 

 ally if we compare the structure of such a form as Fistulipora 

 {Callopora) incrassata, Nich., with that of a form like Propora 

 tuhilata, E. and H. The absence of septa is, however, 

 sufficient to distinguish MonticuUpora from the Helioporidcs. 



^ As before remarked, it is not impossible that "mural pores" may yet be demon- 

 strated to exist in MonticuUpora. This is the more likely, if we remember that 

 these openings have as yet been absolutely demonstrated in only two species of 

 Stenopora J so that some exceptionally well preserved specimen, or some lucky sec- 

 tion, may bring them to light in the MonticuHporoids at any time. 



