Palceozoic Corals from Northern Queensland. 271 



sponding levels in all the corallites, it follows that the tubes 

 are in actual contact with one another at these points only, 

 and that they are separated by ring-like spaces corresponding 

 with all the unthickened segments of the tubes. 



Thin sections of the corallum show different appearances 

 in different portions. Thus, in a transverse section across a 

 branch, the axial corallites are seen to differ in no essential fea- 

 ture of their structure from those of Monticulipora or Favosites. 

 Each possesses its own wall, which is not abnormally thick- 

 ened (fig. 2, B) , the boundary between contiguous tubes being 



Fig-. 2. 



Two tubes of Stenopora ovata, Lonsd., cut transversely across their 

 thickened portions, and showing the contraction of the visceral 

 chamber by an annular deposit of sclerenchyina, which is nof in 

 contact with the wall on one side. B. Two tubes of the same from 

 the centre of a branch, cut across, and showing the thin walls and 

 polygonal form. C. Portion of a tube of the same cut longitudinally, 

 showing the thickening of the wall, the tabulae, and one of the 

 mural pores. Enlarged twenty-five times. Permo-Cai'boniferous, 

 Queensland. 



clearly indicated by a distinct dark line. The tubes in this 

 portion of the corallum are also regularly polygonal, and are 

 certainly, as a rule, in close contact. On the other hand, in 

 sections tangential to the branch and taken a little below the 

 surface, the tubes are cut across in their outer portions, where 

 they are periodically thickened. The tubes still appear to be 

 polygonal and in contact, each being bounded externally by 

 a well-marked dark line ; but the appearances presented by 

 the area within this boundary-line are very puzzling, appa- 

 rently varying according as the section traverses the tubes at 

 the level of their thickened portions or at that of the unthick- 



19* 



