I02 THE GENUS MONTICULIPORA. 



thin walls, are never so far developed as to completely isolate all the larger 

 tubes, and are always provided with more numerous and more closely-set 

 tabulae than is the case in the latter. Spiniform corallites present or absent. 

 Type of the group, Monticii/ipora pdropolifana, Pand. 



{a) Corallites prismatic. {Ex., M. petropolitana, Pand., M. JVhiteavesii, 

 Nich.) 



{b) The large corallites oval or rounded. {Ex., M. calyciila, James.) 



III. MoNOTRYPA, Nich. — Corallites of one kind only, so far as their inter- 

 nal structure is concerned; though there may be well-marked clusters (or 

 " monticules ") of tubes appreciably larger than the average. Corallites usually 

 conspicuously prismatic, their walls thin and apparently structureless, or retaining 

 their primitively duplex character. Spiniform corallites mostly wanting (pres- 

 ent in AL discoidea, James). Tabula complete, uniformly distributed through- 

 out all the corallites, without respect to the size of these ; sometimes nearly 

 obsolete. Type, Montiadipora ujidulata, Nich. 



{a) With thin, apparently structureless walls. {Ex., M. undulata, Nich., 



M. Wiiiteri, Nich., M. irregularis, Ulrich, M. davacoidea, James, I^. 



qiiadrata, Rom., M. calceola, Miller and Dyer, &c.) 

 {b) Walls appreciably thickened, but preserving their duplex character. 



{Ex., M. petasiformis, Nich., M. pukhelia, E. and H., Pil. discoidea., 



James, M. pavonia, D'Orb., M. briarea, Nich., <^'c.) 



IV. Prasopora, Nich. and Eih. jun. — Corallites of two kinds, the smaller 

 ones interspersed throughout the colony, or partially aggregated into clusters. 

 Large tubes with peculiarly incomplete tabulae, which form a series of marginal 

 vesicles, enclosing a lateral or central space, which is usually crossed by a few 

 straight tabulae. Small tubes angular, with numerous complete and close-set 

 tabulae. Spiniform corallites wanting, or very sparingly developed. Walls of 

 the corallites thin and apparently structureless. Corallum usually discoid. 

 Type, Prasopora Graycz, Nich. and Eth. jun. Other examples are M, {Praso- 

 pora) Neivberryi, Nich., and M. {P.) St'hvyiu'i, Nich. 



V. Peronopora, Nich.- — Corallites of two kinds, the larger ones with tab- 

 nice of the same peculiarly incomplete type as in Prasopora. Small tubes with 

 close-set complete tabular. Walls of the corallites thickened, and apparently 

 more or less completely amalgamated, so that their primitive duplex character 

 is lost. Spiniform corallites usually largely developed (apparently wanting in 

 M. vwlesta, Nich.) Corallum laminar or encrusting. Type of the group, J/". 

 frondosa, D'Orb. ( = J/, decipiens, Rom.) Other examples are M. molesta, Nich., 



M. Cincinnaticiisis, James, and probably M. Ortoni, Nich. 



