REPORT ON THE GORGON ACEAN CORALS. 157 



Family Plexaurip^e. 



Euplexaura antipathes Klunzinger. (Plate XV. Figs. 1,2.) 



Plexaura a?itipathes Klunzinger. 



This specimen which is in a dried state, is pale fawn in colour. 



The colony is much branched, the branches arising approximately in 

 one plane. The branches are given off irregularly ; they, in their turn, 

 branch repeatedly, and these branches bear further branches. There 

 are no traces of anastomoses. The basal portions are slightly flattened, 

 but the terminal twigs are round and thicken slightly towards the ends. 

 The branches run close together and fairly parallel. 



The polyp-pores are scattered irregularly over the whole surface, and 

 are not raised above the general level except on the terminal twigs, 

 where they are at the summit of slight conical elevations. They are 

 about 1 mm. apart. 



The cortex is friable, and somewhat thicker on the twigs than the 

 older parts. It is comparatively smooth ; on the older branches there 

 are slight longitudinal furrows which run somewhat spirally round the 

 stem. The axis is of horn, with scattered particles of calcareous matter ; 

 it is of a dense black colour in the thicker branches. 



The " root " portion of the colony shows a great development of a 

 peculiar skeletal substance, hard, and looking like stone. It is dull 

 grey in colour, and shows the same furrowings as the cortex of the stem 

 which extended over it. On treating with acid the stony part is 

 dissolved away, leaving a fine network of horny matter in which the 

 CaC0 3 was contained. 



The grey substance which strengthens the base of attachment is 

 clearly formed independently of the black axis, although it may rightly 

 be regarded as being of the same nature. Judging from the dried 

 specimen it is composed of spicules of lime embedded in a horny matrix, 

 no processes of the coenosarcal canals extending into it, even superficially. 

 It is extremely hard, and breaks with a clean fracture when struck with 

 a hammer. The horny axis, on the other hand, can be cut with a pen- 

 knife. The nature of the horny substance is not determined, but from 

 its insolubility seems similar to the keratin of the axis. It is only 

 rarely seen in specimens of Gorgonacea in Museums, although it is 

 possible that it may be formed at the base of all large Gorgonids when 

 exposed to strong tides. 



