232 



ACTINOZOA. 



waters, than the Zoantharia. Alcyonium has been 

 met with at seventy fathoms, but, like Pennatula, 

 is common in much shallower seas. From so 

 great a depth as 240 fathoms a species of Virgu- 

 laria, V. Finmarehica, was dredged at Oxfjord 

 by M. Sars, who also obtained, in the same locality, 

 the widely different Briarewm grandiflorum, a 

 low creeping Alcyonid, allied to Sarcodictyon. 

 The Gorgonidce, in like manner, seem to prefer 

 deep seas, Corallium having been found at 120, 

 and Gorgonia itself at nearly 200 fathoms. 



Though depths equal to or even exceeding those 

 just mentioned have yielded many species of 

 Zoantharia, Ulocyathns, for example, frequenting 

 water of 200 fathoms, yet, in general, the members 

 of this order are most abundant in seas of not 

 more than 50 to 100 fathoms deep. The Actinidw 

 and Madreporidw include those species which are 

 most prone to descend below this limit. Many 

 of the Actinidce, it is well known, are numerous 

 between tide-marks, the common Sea-anemone 

 tending to encroach upon the line of high water. 



The shallow vertical range of the reef-building 

 Actinozoa has already been sufficiently explained. 

 Certain species are chiefly restricted to particular 

 parts of the reef; Astrceidw and Seriatoporidw 

 choosing its more submerged portions, below the 

 outer exposed edge, upon which Porites and its 

 allies flourish. On the surface of the reef both 

 Astrmidai and Fungidw may readily be distin- 

 guished, the labyrinthic form of Mceandrina, 

 among other genera, being here especially con- 



spicuous 



The soft-bodied 



non-adherent Zoanthai 



usually occur on muddy or sandy banks, at or 



