58 
must have opened over the whole of the upper surface, hut 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 Favosites. This character, however, is much more perceptible by the eye, or w'hen 
the surface is examined with a lens, than it is when thin sections are investigated under 
the microscope, as it is to some extent marked in the latter case by the broken and 
cribriform structure of the walls. Thin sections (PL 3, figs. 7 and 9), whether trans- 
verse or vertical, show that the walls of the tubes are extensively porous and cribriform, 
being pierced by numerous apertures, which place the visceral chambers in direct com- 
munication. Transverse sections also serve admirably to show the character of the 
irregular trabecular sojjta, some of whicli are simply spiuiform, while others divide 
tow'ards their inner extremities, or even unite wdtli their neighbours by their free ends. 
Vertical sections show that the septa are upon the whole placed in longitudinal row's, 
and they exhibit occasionally horizontal trabecula) (PL 3, fig. 9), which maybe regarded 
as of the nature of rudimentary tabula). 
Prom a consideration of the above characters it cannot be doubted that we have 
to deal, in Arcaopora, with a genuine “ Perforate ” Coral, which, however, is closely 
related to the Pavositidae, and may be best jjlaced in this family rather than in any of 
the more regular groups of the Perforata. By the characters of its w'alls and septa the 
genus presents certain alliances with the Poritidse ; but its general form and aspect are 
those of a Favosifes ; and the presence of rudimentary tabula) would further confirm 
the view hero taken. Among the genera of the Pavositida), its nearest ally is to be 
found in the Low'er Silurian genus Columnopora, Nich., which it nearly resembles in 
form and habit. It is distinguished from the latter, however, by the less regularly 
perforate character of its w'alls, by the rudimentary condition of its tabula), and by the 
irregularly dividing and trabecular septa. We are unable to institute any comparison 
between Ar<sopora and the Cretaceous genus Koninckia, E. and H., but the septa of the 
latter seem to bo merely spiniform (six in number) , and the tabuhe are said to be w'ell 
developed and complete. {Nicholson and Ftheridge Jil.') 
Messrs. Waagon and Wentzel have removed Arisopora from the Pavositida) and 
placed it in the Poritidm. It is possible this stop may be quite justifiable. 
Loo. Burdekin Eiver. {The late F. Baintree ; Collu. Brit. Mus.) 
Order— BTJGOSA. 
Pamily— CYSTIPHYLLID^. 
Genus— CYSTIFSTLLFM, Lonsdale, 1839. 
(Murchison’s Silurian System, p. 691. ) 
Cysxiphylltjji AMERiCANirir, Fdw. and Name, var. austeale, var. nov., PL 3, 
figs. 13, 14. 
Obs. Up to the present time we are not acquainted with any published species 
of Cystiphyllum from Australian Devonian rocks, but a species has been met with in the 
Silurian beds of Buriwang, New South Wales. The coral reefs at Hegan’s on the 
Northern Kailway, how’ever, have yielded several examples of a very elongate species, 
with a general resemblance to the British Devonian G. vesiculosum, Goldfuss, but the 
vesicles of the corallum are much too large. On the wdiole the corals appear to come 
nearest to the American form C. americanum, and for all practical purposes may be 
regarded as a variety of it. In only one example has any tendency to a funnel or cone 
shaped outline been observed, such as occurs in C. senecalensc, Billings,* but not 
Canadian Journal, 1859, p. 137. 
