20 THE GENUS MONTICULIPORA. 



(J') Corallites arranged in compact groups, surrounded by " coen- 

 enchyma." 



5. Genus Stellipora, Hall. 



B. Walls of the corallites thick and of lamellar structure. 



(i.) No " coenenchyma." Walls of contiguous corallites amalgamated. 

 (a) " Wandstrange " {7'ide antea) present. 



6. Genus Orbipora, Eichwald. 

 {b) " Wandstrange " wanting. 



7. Genus Monticulipora, D'Orb. (divided into two sec- 



tions, according to the presence or absence of 

 " Porenkanalchen " or " spiniform corallites"). 

 (2.) A reticulate "coenenchyma" present; the lamellae of the walls of 

 the corallites pass directly into the meshes of the " coenenchy- 

 ma." " Wandrdhrchen " (/. ^., spiniform corallites) present. 

 {a) Corallites like one another. 



8. Genus Tretnatopora, Hall. 



{l>) Corallites of two different kinds ; thick-walled corallites alter- 

 nating with thin-walled corallites. 



9. Genus Eittopora, Dyb. 



(II.) The corallum consists of vertical rods, which are united with one another 

 by a series of vesicles. 



10. Genus Labcchia, E. and H. 



As I find myself unable to regard the above classification of 

 the Monticuliporoids as in any way a natural one, and as nearly 

 all the subdivisions proposed in it are, in my opinion, inad- 

 missible, I shall here proceed to analyse the above groups in 

 o-reater detail. 



The genus Dianulites, Eichw. (Dyb.) is defined by Dybow- 

 ski {Joe. cit., p. 15) as including forms with a spherical, hemi- 

 spherical, or botryoidal corallum, the surface being quite smooth 

 or rarely exhibiting eminences. The corallites are more or 

 less irregularly prismatic, of different sizes, the large and small 

 ones irregularly mixed with one another. Tabulae are widely 

 remote, not placed at corresponding levels in different indi- 

 viduals. There is no " coenenchyma," and the corallites are 

 in direct contact with one another. 



I have already (pp. 11, 12) given the reasons which would 

 make me most unwilling to acquiesce in any attempt to revive 

 the genus Dianulites, Eichw. These reasons seem to me to be 

 so strong, that even if the above emended definition of Dy- 

 bowski were found to embrace a natural group of Monticuli- 



