234 ACTINOZOA. 



understood, the many apparent anomalies in the 

 distribution of Coral-reefs, far from being, as 

 some have stated, unaccountable, become in each 

 case susceptible of their appropriate physical 

 explanation. 



In the British seas about ten species of sclero- 

 dermic Zoantliaria occur. The number of Medi- 

 terranean Corals is much greater, though these, 

 with few exceptions, are specifically distinct from 

 those observed by Ehrenberg in the Eed Sea. 

 The Mediterranean also yields two or three forms 

 of sclerobasic Zoantliaria, a group apparently 

 unknown in more northern seas. Corallium 

 rubrum, the Eed Coral of commerce, would seem 

 to be restricted to the same region, though other 

 species of its genus have from time to time been 

 dredged off Madeira and the Sandwich Isles. 



Of Actinozoa, which occur beyond the limits of 

 the Mediterranean and North Atlantic Seas, our 

 knowledge still remains very imperfect, save only 

 in the case of the reef-building Corals and the more 

 conspicuous forms of Ctenophora. The genera 

 Cestum, Callianira, Galyminnaf Chlajeaf and Leu- 

 cothea may be cited as examples of this order cha- 

 racteristic of the tropical and warmer temperate 

 zones. Ocyroe, an obscure but interesting Cteno- 

 phorid, distinguished by the possession of two 

 antero-posterior lobes, prolonged outwards at right 

 angles to the true axis of the body, and which, 

 when better known, may prove to be the imma- 

 ture condition of some apparently dissimilar form, 

 has a range not wider than the equatorial regions 

 of the Atlantic. 



In high latitudes several Actinidce, a few Tiir- 

 binolidcB and Madreporidw, together with various 



