GENERA OF CH.ETETTD^ AND MONTICULIPORIDM. 291 



From Prasopora, Nich. and Eth., jun., Montuulipora is dis- 

 tinguishable only by the very peculiar structure of the tabulae 

 of the former. Lastly, I need not attempt to differentiate from 

 Montictilipora the types known by the names of Dekayia, E. and 

 H., Constellaria, Dana, and Fistulipora, M'Coy [ = Callopora, 

 Hall), as I shall include all these under the former genus, re- 

 taining their titles as of subgeneric value, and shall, therefore, 

 speak of them at greater length hereafter. 



The number of forms included under the comprehensive 

 title of Monticulipora, D'Orb., is so large, and the variations 

 in the minute structure of these are so important, that the 

 genus must of necessity be split up into sections, which may 

 be distinguished by separate names. It is impossible here for 

 me to give anything like a full account of my researches into 

 this subject, and I shall, therefore, content myself with simply 

 giving a brief summary of the general conclusions at which I 

 have arrived, together with short descriptions of some illustra- 

 tive species of the genus. Taking the intimate structure of 

 the corallum as the sole reliable basis for the subdivision of the 

 genus, I propose to include under the general name of Monti- 

 culipora, D'Orb., the following six subgeneric groups, which 

 will be best designated by special titles, and some of which 

 have been previously described as distinct genera. 



I. Heterotrypa, Nich. — Corallites of two or sometimes of 

 three kinds ; the larger ones subpolygonal, partially separated 

 by the development of numerous smaller circular or irregularly- 

 shaped tubes, of which there is no more than a single row. 

 Walls thickened towards the mouths of the tubes. Tabulae 

 conspicuously more numerous in the smaller tubes than in the 

 larger ones. Type of the group the Monticulipora mammulata, 

 D'Orb. (which is also the type of the whole genus). 



II. Dekayia, Edwards and Haime. — Corallites of two kinds, 

 the larger tubes with thin walls, polygonal in shape, and pro- 

 vided with well-developed tabulae. The smaller tubes isolated 

 by the larger corallites, apparently destitute of tabulae, their 

 walls greatly t^hickened, and appearing on the surface as so 



