204 



ACTINOZOA. 



the thecse of the separate corallites do not become 

 lost in the surrounding coenenchyma. In the 

 Poritidoi, on the contrary, such fusion always 

 takes place, and the septal system, instead of 

 forming distinct plates, consists wholly of more or 

 less definite series of trabiculae. The entire 

 corallum, in like manner, appears to be made up 

 of a spongy, reticulate sclerenchyma. 



The next division, Tiibulosa, contains only a 

 single family, Auloporidce ; and this but two 



Fig. 36. 



ZoANTHARiA SCLERODEEMATA : — tt, corallum of TicvhinoUa 

 costata; b, the same, in transverse section, showing the columella, 

 septa, theca, and costse ; c, part of corallum of Aulopora tubcefor- 

 mis, (All, except c, magnified), 



genera, Pyrgia and Aidopoi^a, in both of which 

 the corallite, while destitute of tabulse, has its 

 septal system indicated by faint markings along 

 the inner surface of a comparatively smooth tube. 

 Pyrgia is simple, though having a distinct epi- 

 theca. In Aulopora the somewhat remote coral- 

 lites are connected by means of a basal creeping 

 coenenchyma. (fig. 36, c.) 



The four last families of Zoantharia constitute 



