128 CORALS 



be recognised at once by the fact that the stems and 

 branches are considerably flattened and by its brihiant 

 scarlet colour. Specimens over four feet in height have 

 been found. 



In the West Indies the most conspicuous members of 

 the family are Leptogorgia, Pterogorgia, and Xiphigorgia, 

 which form great tufts of long flexible branches frequently 

 adorned with brilliant purple, red, and yellow colour. In 

 Leptogorgia and Pterogorgia the polyps are arranged 

 laterally on the branches, and between them in dried 

 specimens there is a shallow longitudinal groove. In 

 Pterogorgia the polyps when retracted are protected by 

 well-marked verrucae ; in Leptogorgia the verrucae are very 

 small and not raised above the level of the coenenchym. 

 In Xiphigorgia the position of the polyps is indicated in 

 dried specimens by three or four prominent ridges without 

 verruciform swellings. 



The genus Phyllogorgia, also found in the West Indies, 

 is characterised by the leaf-like expansion of the branches of 

 its flabelliform colony. 



The family Gorgonellidae includes a large number of 

 genera many of which have a close resemblance to the 

 Gorgoniidae. The coenenchym is usually thin and the posi- 

 tion of the retracted polyps indicated by low mounds or 

 verrucae. The only constant difference between the two 

 families is that the horny axis is impregnated with calcareous 

 matter. 



To determine therefore whether a given specimen is a 

 Gorgoniid or a Gorgonellid the first test is to place a piece 

 of the axis, thoroughly well cleaned of its coenenchym, in 

 nitric or hydrochloric acid. If it is a Gorgonellid it will 

 give off bubbles of carbon dioxide, and if it is a Gorgonud 

 it will not. 



JuxcELLA. — One of the most interesting of the Gor- 

 gonellids is Juncella, in which the long brown cylindrical 

 axis is usuallv unbranched and sometimes has a length of 

 several feet and is as thick as a finger. When fresh the axis 

 is covered with a red or orange coloured coenenchym of 



