2 8o TABULATE CORALS. 



of which became closed by secondary deposit as the corallum 

 assumed its final characters. Nor have I any doubt that the 

 spines of forms like M. moniliformis, Nich. (figs. 36, 37), M. 

 Jamesi, Nich., M. tumida, Phill., M. gracilis, James, and others, 

 are similarly peculiarly modified corallites, the mouths of which 

 become finally closed. A further evidence of this is to be 

 found in such species as M. frondosa, D'Orb., in which the 

 spines do not appear as spines upon the surface, though thin 

 sections exhibit appearances precisely similar to what has been 

 indicated as occurring in the forms alluded to above. On the 

 contrary, the spines remain permanently open, and appear on 

 the surface as minute thickened apertures between the ordinary 

 calices, so that they have been both recognised and figured as 

 a special group of corallites (Ann. and Mag. Nat. Hist, ser. 4, 

 vol. xviii. p. 92, PI. V., fig. 1 1). Lastly, if we admit the prob- 

 able correctness of the views here advanced, we have a very 

 interesting analogy established between certain forms of Monti- 

 culipora and some of the species of Stenopora, Lonsd., in which 

 structures of a precisely similar nature occur. Thus, if we 

 examine a tangential section of Stenopora Tasmaniensis, Lonsd., 

 taken just below the surface (fig. 38), we see that the surface- 

 spines are continued inwards precisely as they are in Monti- 

 culipora moniliformis and allied types, while they are similarly 

 composed of concentrically-disposed lamellae of dense scleren- 

 chyma. The central cavities of the spines seem, however, to 

 be more or less completely obliterated with age ; and the coral- 

 lites in the outer portion of their course (fig. 38, A) exhibit the 

 annular thickenings of their walls which are so characteristic of 

 the genus Stenopora. In spite of these differences, the resem- 

 blance between the spines of the Monticuliporcs above alluded 

 to and the similar structures in certain species of Stenopora is 

 so striking that one can hardly resist the conviction that there 

 must subsist between the two a relationship of real affinity. 



More conspicuous, more generally familiar, and more uni- 

 formly present than the spines, are those structures in the 

 Monticulipora, which are known as " monticules " and " macu- 



