ACTINOZOA. 199 



tionally larger than in most of the Adinidce 

 proper. The base is either rounded or bluntly 

 tapering, and, in certain genera, becomes at times 

 much distended, as in Saccanthus or Edwardsia. 



In some the base is furnished with a central 

 perforation : in others this appears to be wanting. 

 In Peackia the oral region is singularly modified ; 

 the tubercles of its single groove uniting to form 

 a tube, the expanded summit of which, * conchula ' 

 of Mr. Grosse, presents a more or less thickened, 

 everted edge, cleft into a variable number of lobes. 



The polypes of the Zoantliidce and true coral- 

 ligenous Zoantharia, save in characters merely 

 generic, resemble those of the Actinidce. Their 

 average size is, perhaps, smaller, though the Ac- 

 tinia Pawnotensis of the Pacific, whose expanded 

 disc measures a full foot in diameter, is, in this 

 respect, certainly exceeded by large specimens of 

 Fungia. This genus presents a widely extended, 

 circular or elliptic disc, destitute of the usual 

 folding margin, and blending, by insensible de- 

 grees, with the shallow, ill-defined column, over 

 the radiating septa of which the tensely stretched 

 soft parts converge towards the prominent, central 

 mouth. Such a simple form contrasts strikingly 

 with Meandrina and those allied genera in which 

 the several polypes produced by fission fuse to- 

 gether into a convoluted linear track, with tentacles 

 arising from its opposite sides. 



Of these appendages and their variations, a 

 brief notice seems here required. In Anthea 

 {=Anemonia) they are long and slender; in 

 Fungia and Discosoma, reduced to mere warts 

 or papillae; in Capnea, very short, resembling 

 oblong tubercles ; while in Arachnactis, the outer 



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