104 



COELENTERATA ANTHOZOA 



SUB-BRANCH II 



by the smaller (mesopores), and hence are completely separated from one another. 

 Occasionally, in addition to the preceding, a further series of tubes called 

 (icanthopores occur, which are thick -walled and form small tubercles on the 

 surface. Extraordinarily abundant in Ordovician and Silurian, particularly the 

 former ; rarer in Devonian and Triassic. 



Nicholson compares the mesopores of Monticulipora with the siphonopores 

 of Heliopora, and supposes the corallum to have been inhabited by dimorphous 



FIG. 186. 



Enlarged tangential sections parallel to 

 external surface. A, Monticulipora (Hetero- 

 trypa)pukhella, E. and H. B, M. (Heterotrypa) 

 ramosa, E. and H. (after Nicholson). 



FIG. 187. 



Monticulipora (Diplotrypa) Petro- 

 politana, Panel. Ordovician ; St. Peters- 

 burg. Enlarged tangential section 

 parallel to external surface (after 

 Dy bow.sk i). 



polyps. F. Eoemer holds the smaller tubes for immature corallites formed by 

 budding. The following sub-genera are recognised by Nicholson : 



a. Heterotrypa, Nich. (Figs. 185, 186). Corallites of two kinds, the larger- 

 ones sub-polygonal, and separated by a single row of mesopores. Walls 



FIG. 188. 



Prasopora Selwynii, Nich. Ordovician ; 

 Ontario. A, Tangential section parallel to ex- 

 terior. B, Vertical section, enlarged. C, Auto- 

 pores ; t, Tabulae; t', Cystoid tabulae (after 

 Nicholson). 



FIG. 189. 



Neuropora angulosa, Goldf. sp. Upper Jur- 

 assic ; Oerlingen, near Ulm. A, Portion of ex- 

 ternal surface enlarged. B, Corallum, natural 

 size. 



thickened towards mouths of tubes ; tabulae horizontal ; acanthopores generally 

 present. 



b. Monotrypa, Nich. Corallites all similar, or of two kinds, not conspicuously 

 different in size, and usually polygonal and thin -walled. Ordovician to 

 Devonian, also Triassic. M. Itecubariensis, Schaur. sp. 



c. Diplotrypa, Nich. (Dianulites, Eich.), (Fig. 187). Corallites of two kinds, 

 uniformly thin-walled ; the autopores aggregated into clusters or monticules, 

 but also scattered with the mesopores throughout the colony. Ordovician. 



d. Prasopora, Nich. (Fig. 188). Corallites of two kinds, uniformly thin- 

 walled ; mesopores with numerous horizontal tabulae, autopores with incomplete 

 and cystoid tabulae. Ordovician and Devonian. 



e. Peronopora, Nich. Like the preceding, but thick-walled. 



