ALCYONARIAN CORALS 133 



contain any genera that are very well known, and most 

 of them are to be considered among the rarities of museum 

 collections. 



The Muriceidae is a very large and difficult family 

 showing great variety in form, colour, and habit. The 

 most noticeable character is that the surface of the coen- 

 enchym and of the polyps is usually armed with minute 

 spines, so that it is rough or harsh to the touch. This is 

 due to the fact that many of the spicules at the surface are 

 relatively large and provided with spines which project 

 through the ectoderm (Fig. 45 D, p. 105). 



The Chrysogorgiidae are almost entirely confined to deep 

 water, and are very rare. In a large proportion of the 

 species the spicules are thin oval or hour-glass plates. This 

 character of the spicules has suggested to some authors 

 that the Chrysogorgiidae are the most primitive of all the 

 Gorgonacea, but it is possible that this and other characters 

 may be associated with the life in the slow uniform currents 

 of deep water, and a sign of special adaptation rather than 

 of primitive features. 



Ceratoporella.^ — A very remarkable coral was obtained 

 by the naturalists of the American Blake Expedition in 100 

 fathoms of water off Cuba, the zoological position of which 

 was difficult to determine-. 



The single unique specimen consists of a lump of very 

 hard limestone perforated by boring sponges in various 

 directions. Projecting from one side of this lump there is a 

 mushroom-shaped process capped by a thin brown lamina, 

 circular in outline and 42 mm. in diameter, composed of 

 short vertical tubes. There seems to be little doubt that 

 the whole lump of coral was formed by the successive growth 

 of the organisms that constructed the short brown tubes at 

 the surface (Figs. 61 and 62). 



1 See Hickson on " Ceratopora," Proc. Roy. Soc, 191 1, vol. 84, p. 195. 

 The name Ceratopora, being preoccupied, was subsequently changed to 

 Ceratoporella. 



