44 THE GENUS MONriCULIPORA. 



III. Surface-chai'actcrs. — As regards the surface-characters 

 of the MonticuHporoids, the appearances presented by the 

 caHces vary according as we have to deal with a form in which 

 the walls of the corallites remain permanently more or less 

 thin throughout their entire extent, or with one in which the 

 tubes underoTQ a marked thickenino- before reachinor the surface. 

 In the former of these cases the calices are polygonal and 

 sharp-edged, and thus resemble the calices in a Favosites of 

 normal type. In the second case, the calices are rounded, oval, 

 or subpolygonal, and exhibit thick and rounded margins — 

 reminding us, so far as this particular character goes, of the 

 calices of a Pachypora or a Stenopora. Monticulipora petro- 

 poliiaua, Pand., and its allies, may be taken as exemplifying 

 the former condition; while M. ramosa, D'Orb., J/, maimnu- 

 lata, D'Orb., M. frondosa, D'Orb., M. Jamesi, Nich., M, 

 tumida, Phill., and many others, are examples of the latter 

 state of parts. 



Apart, however, from the mere characters of the calices, there 

 are certain special superficial features present in various Mon- 

 ticuliporoids, either singly or in combination, which demand 

 special consideration. Foremost amongst these are the struc- 

 tures which are known as " monticules" or " mamelons," from 

 the presence of which, in many species, the name of Monticu- 

 lipora is derived. The " monticules," in their most typical 

 form, are circumscribed areas on the surface of the corallum, 

 which are more or less elevated above the general level, so as 

 to constitute a series of rounded, oval, or elongated eminences. 

 Sometimes the "monticules" are composed of corallites which 

 differ in no conspicuous feature from those which form the 

 mass of the corallum {e.g., in AI. rainosa, D'Orb., and AI. Cin- 

 cin7iaticnsis, James), and it is generally in such cases that these 

 eminences are most conspicuous and prominent. In other 

 cases {e.g., M. pidchella, E. and H.), the corallites which form 

 the " monticules " are markedly larger than the average ; but 

 in such cases the monticules hardly deserve the name, as they 

 are scarcely or not at all elevated above the general surface. 



