384 



COELENTERATA — ANTHOZOA 



ramified (Fig. 166), and in some cases very long (Actinodendron 

 arhoreum). Many of the specimens of A. plumosum and 

 Megalactis griffithsi are of very large size, 8 to 12 inches 



in diameter. Of the 

 former of these two 

 species Saville Kent 

 remarks : " The 

 colours are lacking 

 in brilliancy, being 

 chiefly represented 

 by varying shades 

 of light brown and 

 white, which are 

 probably conducive 

 to its advantage by 

 assimilating it to 

 the tint of its sandy 

 bed. When fully 

 „,.,,,.,, , r, J' <■ ** < extended the com- 



FiG. 166. — Actiiioaendron plumosum. D, disc of attaoli- 



ment ; Si, siphonoglyph ; U t, lobes of the marginal disc pound tentacles are 



bearing the tentacles ; IF body- wall. Height of the elevated tO a height 

 column 200 mm. (After Haddon.) 6 



of 8 or 10 inches, 

 and bear a remarkable resemblance to certain of the delicately 

 branching, light brown sea-weeds that abound in its vicinity." 

 The same author calls attention to their stinging, which is 

 " nearly as powerful as the ordinary stinging nettle." 



Order III. Madreporaria. 



The Madreporaria form a heterogeneous group of Zoantharia 

 characterised by a single common feature, the formation of an 

 extensive skeletal support of carbonate of lime. In a great 

 many cases the skeleton exhibits cups or " calices " into which 

 the zooids may be completely or partially retracted, and these 

 calices usually exhibit a series of radially disposed vertical 

 laminae, the "septa," corresponding with the inter -mesenteric 

 spaces of the zooids. Calices and structures simulating septa 

 also occur in Heliopora, which is an Alcyonarian, and in certain 

 fossil corals which are probably not Zoantharians. The anatomy 

 of the zooids of a great many Madreporaria is now known, and, 



