2S2 TABULATE CORALS. 



plete." The only exception to the latter part of this statement 

 with which I am acquainted is the curious M. frondosa, D'Orb., 

 in which the tabulae seem to have the form of crescentic dia- 

 phragms, with an excentric aperture or perforation on one side. 

 As a rule, the tabulae are very sparsely developed in the axial 

 and deeper portions of the corallum, and become much more 

 numerous as the tubes approach the surface. As a rule, also, 

 the tabulae are conspicuously more numerous and more closely 

 set in the smaller corallites of the two sets of tubes of which the 

 corallum is normally composed. In a few forms, lastly, the 

 tabulae may become curved, so as to assume a subvesicular or 

 vesicular aspect ; but this is quite an exceptional feature. 



With regard to " septa " in the Montic7ilip07'cE, it need only 

 be said that no traces of these structures have hitherto been 

 detected in any Monticuliporoid. Occasionally one may see 

 in thin transverse or tangential sections a single azygous septum 

 projecting for some distance into the interior of a tube, but this 

 seems to be really the result of fission of a corallite, as we have 

 seen to be the case in Chcctetcs. 



As regards the dcvclopiiient of the JMonticiilipora; I have little 

 to say from actual observation, and that little will be best said 

 after I have given some account of the views held upon this 

 subject by Dr Gustav Lindstrom (Ann. Nat. Hist., sen 4, vol. 

 xviii. p. 5 ct seq.) As I find myself in this matter unable to 

 accept the conclusions of the distinguished Swedish palaeon- 

 tologist, it is only just that I should quote his account of the 

 development of Monticzdipora at length. Upon this point he 

 remarks : — 



"If numerous specimens of the common M. petropolitana, 

 Pand., be closely scrutinised, it will be seen that its semi-globose 

 colony, so closely resembling a Favosites in its initial develop- 

 ment, has an origin that could hardly be suspected. It begins, 

 indeed, as a Bryozoon, as a Discoporella, as what Hall has 

 termed Ceramopora imbricata (Pal. N.Y., vol. ii. p. 169, PI. 40 

 E, figs. I a-\ i). There can be no doubt that this is closely 

 allied to the r&c&nt Discoporella (see Fr. Smitt, Ofv. Vet. Akad. 



