198 THE GREAT BARRIER REEF. 



A second species of the fringe-tentacled Xenise, which is abundantly represented on the 

 Barrier reefs, very much resembles in its external aspect the variety Xcitin ochracca, described in a 

 previous paragraph. The polypary is commonly a pale pinkish stone-colour, and the distinctly- 

 fringed polyp-tentacles are a decided brown. No pulsating motion, as in the type last described, 

 is exhibited by this species. The aggregated polyparies of this form not unfrequently cover 

 very extensive areas on the reefs ; and when, as commonly happens, they grow under such 

 conditions that they are left, on the retreat of the tide, in natural pools, with only a few inches of 

 water over them, their expanded sheaf-shaped coralla and extended polyp-stars present a remark- 

 ably pleasing spectacle. An illustration of an expanded polypary of this species, together 

 with a magnified polyp, is included in Figs. 15 and 15A of Chromo plate X., and, in the 

 absence of discoverable evidence of its previous description, it is herein associated with the 

 title of Xcnia bniiinca. Concerning the genus Xenia, collectively, it is undoubtedly desirable, 

 for purposes of systematic classification, that the two distinct natural series represented by 

 the fringed-tentacled and warted or tuberculate-tentacled species should be generically separated. 

 As the fringed-tentacled series, typified by the Red Sea, Xcnia umbellata, of Savigny and 

 Lamarck, possesses the more valid claim to the original generic title, a new one, that of 

 Paraxenia, is herewith proposed, for the reception of those forms, such as Xcnia elongata and 

 X. ochracca, previously described, in which tentacle-pinnules are represented by minute wart- 

 like prominences, which probably perform an adherent or suctorial function. 



A small group of the Alcyonaria remains to be noticed, in which the polyps, in place of 

 being bound together in such a manner as to form a more or less compact corallum, are simply 

 held in union with one another through the medium of a common creeping root, or stolon, out of 

 the substance of which new polyp-buds are continuously developed. These proliferous roots, or 

 stolons, may so ramify or interlace with each other as to form a thickly-matted polypary, under 

 which conditions the expanded polyps appear, from a surface view, to arise as in the preceding 

 species from a common, compact base. This structural modification is appositely illustrated by a 

 type, Clavularia viridis, that is very abundant on the reefs, in the vicinity of Thursday Island and 

 throughout Torres Strait. The species, delineated in Fig. 17 of Chromo plate No. X., is an 

 exceedingly handsome one; and the individual polyps, for an Alcyonarian, are of considerable size. 

 The expanded tentacular crown measures as much as an inch to an inch and a half in diameter, 

 and is mounted on the summit of a subcylindrical or clavate stalk, which springs perpendicularly 

 from the prostrate stolon. The component tentacles in this type are remarkable for the length 

 and luxuriant development of their secondary branchlets, or pinnules. These slender filamentous 

 pinnules are very frequently of a bright golden-green colour ; and, where the polyps are thickly 

 massed together, they so completely conceal all other structural details from view, that the 

 colony-stocks present the appearance of waving tufts of living moss. The creeping stolon, 

 the erect stalk or column, and the central shafts ol the tentacles of this species, are usually a light 



