172 TABULATE CORALS. 



Mr R. L. Jack, F.G.S,, in Queensland ; and having made a 

 careful microscopical examination of the genus by means of 

 thin sections, I am able not only to confirm De Koninck's 

 reference of the genus to the Favositidcs, but to show further 

 that its characters are entirely peculiar, and such as to separate 

 it generically from all the other members of the family. The 

 specimens in question formed part of a collection of Australian 

 corals which will shortly be described by Mr Robert Etheridge, 

 jun., and myself; and it is to the kindness of my colleague that 

 I owe the permission to use here the previously given generic 

 diagnosis, as well as the following observations upon the struc- 

 ture of Stenopora. Pending the publication of our joint memoir, 

 however, I shall not add in this place any descriptions of the 

 species, merely remarking that the forms which we have ex- 

 amined appear to be referable to three species, one of which 

 is identical with S. ovata, Lonsd., while a second seems to be 

 new {S. Jackii, Nich. and Eth. jun.), and the third is not in a 

 condition to admit of definite specific identification. 



Obs. — Taking 6^. ovata, Lonsd., as the basis of the following re- 

 marks, the corallum in Stenopora is usually more or less branched; 

 but the branches may be so thick, and may so extensively coal- 

 esce, that its general form becomes that of a lobate mass. The 

 corallites (fig. 25, a) radiate in all directions from an imagin- 

 ary axis, and present very different appearances in the central 

 and circumferential portions of the corallum respectively. In 

 the axial portion of the branches the tubes are nearly vertical, 

 have thin walls, are essentially polygonal or prismatic in shape, 

 and are nearly or quite in contact with one another throughout. 

 As they pass upwards, the tubes gradually diverge, coming at 

 last to be nearly horizontal, and continuing in this direction for 

 some distance, till they at last open upon the surface. There 

 is thus an outer zone of the corallum in which the corallites are 

 nearly transverse to the axis of the branches, and within this 

 zone they present all their peculiar features. In this region, 

 namely, the corallites (fig. 25, b) assume a generally cylindrical 

 appearance, owing to the fact that their walls are thickened at 



