226 On Palaeozoic Corals from Northern Queensland. 



or, where the corallites become a little separated from one 

 another, these may be increased in number. Septa almost 

 obsolete, thread-like. A specimen measures 5 inches by 4. 



Obs. The form and arrangement of the ccenenchymal tubuli 

 render the present species a very interesting one. If hori- 

 zontal sections in the mass are examined only with the naked 

 eye or ordinary lens, the species will be pronounced a 

 Plasmopora ; and this it at first appeared to us to be. It has 

 all the general appearance of this genus, especially in the fact 

 that there is often but a single row of oblong interstitial tubes 

 between every two corallites. In such sections the walls of 

 these tubes have quite the appearance of thread-like costse 

 radiating from corallite to corallite, or bifurcating at various 

 angles where their number is increased between the corallites, 

 as in Plasmopora. When, however, vertical microscopic 

 sections are examined, the true affinities of this peculiar coral 

 at once become apparent. In the first place, the arched and 

 vesicular tabula} of Plasmopora are wanting, and Ave find in 

 their place the straight horizontal diaphragms of Heliolites. 

 Secondly, in similar sections the interstitial or ccenenchymal 

 structure is found not to consist of vertical canaliculi formed 

 by the irregularly- developed walls of the tubuli, and sub- 

 divided by horizontal or convex dissepiments into irregularly 

 formed cells, as in Plasmopora, but of a series of small regular 

 and well-developed cells formed by the intersection of the 

 vertical tubuli and their horizontal tabular, which are 

 usually placed on the same level and correspond with one 

 another, precisely as seen in vertical sections of Heliolites 

 megastoma, M'Coy. 



In working out this interesting coral we have made a series 

 of microscopic sections of Plasmopora petaliformis and Helio- 

 lites megastoma, for comparison with those of the Queensland 

 fossil ; and these have enabled us to indicate Heliolites as the 

 proper resting-place for this otherwise very Plasmopora-Wka 

 coral. 



So far as our investigations enable us to form an opinion, II. 

 plasmoporoides is most nearly allied to H. megastoma, M'Coy ; 

 indeed, in the figure of this species given by Edwards and 

 llaiine we notice the one-celled disposition of the ccenen- 

 chyma in places, similar to that seen in the present species. 

 The latter, however, is clearly distinguished from H. megastoma. 



Locality and Horizon. Broken River, a tributary of the 

 Burdekin River, North Queensland. Devonian Limestone. 



Collector. The late R. Daintree, Esq. 



[To be continued.] 



