278 Dr. H. A. Nicholson and Mr. R. Etheridge, Jun.,<m 



ginary axis to open upon the upper surface of the colony. 

 Under surface covered with an epitheca (?). The corallites 

 are firmly united by their walls, which are extensively pierced 

 by apertures, placing the visceral tubes in direct communica- 

 tion. Septa trabecular, often irregularly divided, or anasto- 

 mosing at their free ends. Tabula? rudimentary, represented 

 by occasional horizonal trabecular. No columella nor ccenen- 

 chyma. 



Obs. This genus is founded upon a single remarkable 

 specimen belonging to the " Daintree collection," from the 

 Devonian or Carboniferous deposits of Queensland, which we 

 propose to distinguish specifically by the name of Arceopora 

 australiSj and of which we subjoin a brief description. 



Arceopora australis, Nich. & Eth., Jun. 



Spec. char. Corallum massive, pyriform, of considerable 

 size, composed of polygonal or prismatic corallites which 

 radiate outwards from an imaginary axis to open on the upper 

 surface of the colony. Average diameter of the corallites from 

 two thirds to three fourths of a line, no very small tubes being- 

 intercalated amongst those of ordinary dimensions. Walls 

 amalgamated, irregularly cribriform. Septa variable in num- 

 ber, spiniform, or irregularly divided. Tabular rudimentary. 



Obs. The corallum of A. australis might at first sight be 

 readily taken for that of any of the larger and more massive 

 species of Favosites (such as F. hemisphcericus, Yand. & 

 Shum.), though even to the naked eye the absence of distinct 

 tabular and the cribriform or porous condition of the walls 

 are striking features. Our only specimen is not perfect, and 

 is not only completely silicined, but is thoroughly infiltrated 

 with silica tinged with oxide of iron. Its height is rather more 

 than three inches, and its greatest width something over four 

 inches. Its form is pyriform, the narrow base having evidently 

 been attached to some foreign body, while the under surface 

 was almost certainly covered by an epitheca, of which no traces 

 now remain. The calices must have opened over the whole 

 of the upper surface ; but none of them are preserved in the 

 specimen now before us. The corallites radiate with a 

 graduated divergence from the imaginary axis of the colony ; 

 and their form is regularly prismatic or polygonal, as in Favo- 

 sites. This character, however, is much more perceptible by 

 the eye, or when the surface is examined with a lens, than it 

 is when thin sections are investigated under the microscope, 

 as it is to some extent masked in the latter case by the broken 

 and cribriform structure of the walls. Thin sections (fig. 3, 

 A & B), whether transverse or vertical, show that the walls of 



