COL UMNARIAD^. 1 93 



and 2), and weathered or roughly-fractured surfaces sometimes 

 exhibit the exterior of the tubes. No evidence has been ob- 

 tained by thin sections, or otherwise, as to the existence of 

 "mural pores," and it must therefore be presumed that the 

 walls are imperforate. 



The septa (PI. X., figs, i and 2) are well developed and 

 lamellar, extending from the top to the bottom of the visceral 

 chamber, and reaching more or less nearly to the centre of the 

 tube, which they do not quite reach. There is sometimes a 

 curious irregularity of the septa, one or more being predomi- 

 nantly developed, and there are also two distinct sets of these 

 structures, a long and a short series, alternating regularly with 

 one another. Lastly, the tabulae are very numerous and well 

 developed, being complete and more or less horizontal, and not 

 placed at corresponding levels in contiguous tubes. 



The affinities of the genus Cohmmaria are still very obscure. 

 If a more extended examination of specimens by means of thin 

 sections, with special reference to this point, should show the 

 walls to be really imperforate, as we must at present conclude 

 them to be, and as they probably really are, then we cannot 

 place the genus in the Favositidce. Nor is there any other 

 group among the old " Tabulate Corals " of Milne-Edwards 

 and Haime to which they could be referred with any greater 

 propriety. The genus, indeed, is much more like one of the 

 Rugosa than one of the " Tabulatay It possesses well- 

 developed and lamellar septa (in its type-forms at any rate), 

 and its tabulae are hardly better developed than in several 

 undoubted Rugose corals (such as Amplexiis, Diphyphyllum, 

 &c.) In fact, it might be at once, and without any violence, 

 placed in the Stauridce, close to Stauria, except that there is no 

 predominant development of four of the septa. On the other 

 hand, the genus has many points of likeness with Lyopora, 

 which has no Rugose affinities to speak of. Upon the whole, 

 therefore, it seems impossible at present to assign any definite 

 systematic place to Cohunnaria, and we must regard it as the 



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