1 68 TABULATE CORALS. 



" Perforate " coral, which, however, Is closely allied to the 

 Favosi tides, and may be best placed in this family rather than 

 in any of the more regular groups of the Perforata. By the 

 characters of its walls and septa the genus presents certain 

 alliances with the Poritida, but its general form and aspect are 

 those of a Favosites, and the presence of rudimentary tabulae 

 would still further confirm the view here taken. Among the 

 genera of the Favositidce, Arcsopora finds its nearest ally in the 

 Lower Silurian genus Coliinniopora, Nich., which it nearly re- 

 sembles in form and habit. It is distinguished from the latter, 

 however, by the less regularly perforate character of its walls, 

 by the rudimentary condition of its tabulae, and by the irregu- 

 larly-dividing and trabecular septa. I am unable to institute 

 any comparison between Arceopora and the Cretaceous Kon- 

 t7ickiay E. and H., but the septa of the latter seem to be 

 merely spiniform (six in number), and the tabulae are said to 

 be well developed and complete. 



The geological horizon of Ar^opora Attstralis, Nich. and 

 Eth. jun., is not quite certain, but it occurs in deposits of 

 Devonian or Carboniferous age (the former most probably) 

 in Queensland. 



6^^;^?/^ S TEND FOR A, Lousdale, 1844. 



(Appendix to Darwin's Volcanic Islands, p. 161, 1844, and in Strzelecki's 

 Phys. Hist, of New South Wales, p. 262, PI. VIII., 1845.) 



Tnbidiclidia, Lonsdale, in Murchison's Geol. of Russia, p. 601 (note), 1845. 

 (Non Stenopora, M'Coy, Brit. Pal. Foss. p. 24, 185 1.) 



Gen. Char. — Corallum ramose, or sublobate, rooted below, and 

 composed of tubular corallites, which are nearly vertical in the 

 centre of the branches, and radiate outwards from an imaginary 

 axis to open on all points of the free surface. Corallites in 

 the centre of the branches, polygonal, thin-walled, and more or 

 less completely in contact ; but in the outer curved portion 

 of their course, more or less cylindrical, and annulated by 



