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 
acunthopores 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 J/onticulipora with the siphonopores 
of Heliopora, and supposes the corallum to have been inhabited by dimorphous 







Fic. 187. 
Fia. 186. Monticulipora (Diplotrypa) Petro- 
Enlarged tangential sections parallel to politana, Pand. Ordovician; St. Peters- 
external surface. A, Monticulipora (Hetero- burg. Enlarged tangential section 
trypa) pulchella, E. and H. B, M. (Heterotrypa) parallel to external surface (after 
ramosa, BE. and H. (after Nicholson). Dybowski). 
polyps. F. Roemer 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 

D? locas Fic. 189. 
Prasopora  Selwynii, Nich. Ordovician ; 
Ontario. A, Tangential section parallel to ex- ~ Neuropora angulosa, Goldf. sp. Upper Jur- 
terior. 6, Vertical section, enlarged. C, Auto- assic; Oerlingen, near Ulm. 4A, Portion of ex- 
pores; t, Tabulae; ¢’, Cystoid tabulae (after ternal surface enlarged. /, Corallum, natural 
Nicholson). 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. Recubariensis, Schaur. sp. 
c. Diplotrypa, Nich. (Dianulites, Bich.), (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. 
