THE MOXTICULIPOROIDS. 



351 



225, b). In other cases, one half of the tube is crossed by straight 

 tabulae, while the other half is occupied by curved or " cystoid " 

 tabulae, forming a series of lenticular vesicles on one side (fig. 

 230, f). In other cases (Prasopora), "cystoid" tabulae are devel- 

 oped all round the periphery of the tube, and the centre is occupied 

 by straight tabulae. Lastly, in Fistulipora, the walls of the meso- 

 pores are incompletely developed, and the tabulae unite to form a 

 tissue of lenticular vesicles between the autopores, the genus thus 

 bearing the same relation, in this respect, to Callopora that Plasmo- 

 pora does to Heliolites among the Heliolitidce. 



The great majority of the Monticuliporoids exhibit no radial 

 structures in the tubes which could be compared with the " septa " 

 of an ordinary coral. In a few forms, such structures do occur, but 

 it is doubtful if in any such instance we have to deal with structures 

 really developed in mesenteries, and therefore really homologous 

 with the " septa " of the Zoantharia. Thus in Fistulipora^ each 

 autopore is provided with two longitudinal folds, situated opposite 

 one another, towards one end of the visceral chamber. Again, in 

 a hitherto undescribed species of Callopora (fig. 229, a) each 



Fig. 229. — a. A large specimen of Callopora Foordii, of the natural size ; b, Tangential section 

 of the same, showing thepseudoseptal folds in the autopores, enlarged twenty times ; c, Vertical 

 section of the same, similarly enlarged, a, Autopores ; m, Mesopores. From the Ordovician 

 rocks of Esthonia. (Original.) 



autopore is provided with from two to five radial plications of the 

 wall, which closely resemble the " septa " of Tetradium, and give a 

 characteristic floriform appearance to cross-sections of the corallites. 

 Moreover, in typical examples of Monticulipora mammulata, D'Orb. 

 ( = Peronopora moksta, Nich.), the author has detected radially dis- 

 posed spines (fig. 230, d), which have much the appearance of the 

 radial spines of Favosites and Syringopora ; and similar structures 

 have been recognised by other observers in other forms. 



Lastly, as regards the mode of growth of the skeleton, new tubes 

 are most usually produced by " intermural gemmation/' in a manner 



