1 82 THE GREAT BARRIER REEF. 



96), flourished as far south as Moreton Bay. As with the Stags'-horn variet}', Madirpora licbcs, 

 previously described, although much more frequently, these two species may occupy the greatest 

 portion of the tidally-exposed reef-surface, covering acres as far as the eye can reach. Such a 

 luxuriant development of Madirpora convcxa is characteristically illustrated by the photographic 

 reef-view reproduced in Plate IX., and to a lesser degree in Plate X., No. 2. The living 

 colony-stocks of this species, as shown in Plate IX. consist at every stage of development, of 

 flattened, slightly convex, expansions, and these may be several feet in diameter. The visible 

 upper surface is composed of short, erect, subdividing branchlets, which, springing from a more 

 or less massive basis, formed by the coalescence of the primary branches in a horizontal plane, 

 rise approximately to the same level. The increase in size of these coralla, as shown by the 

 specimens in the reef-view named, is accomplished by the outgrowth of the peripheral border. 

 A type very closely allied to both Madirpora millepora and M. convcxa, but having a more 

 conspicuously flattened corallum, is distinguished by the title of Madrepora prostrafa. Fragments 

 of two colony-stocks of this species are delineated with their living colours in Figs, i and 2 of 

 Chromo IX. As here demonstrated, the colours of the living coralla vary considerably. As they 

 most abundantly obtain, the basal portions of the coralla, together with the greater area of 

 the erect branchlets, one of a dark-fawn or a red-brown hue, while the distal terminations of the 

 branchlets are pale greenish- or primrose-yellow. In other colony-stocks, the basement and erect 

 branchlets, excepting at their tips, are either a light buff-brown or a bronze-green, the terminal 

 half-inch or so, as in the previously-described variety, being light yellow. In rarer instances, 

 coralla have been met with in which the basement was fawn-coloured, and the corallites a bright 

 rose-pink, excepting those of the terminal quarter of an inch, which were bright lemon-yellow. 

 The polyps with their extended tentacles, in this rose-tinted variety, were pale yellow throughout ; 

 in the commoner varieties, previously described, they were usually pale emerald-green. In 

 another somewhat abnormal variety of this very variable species, the branchlets were a dark 

 sage-green, the terminal corallites and the edges of many of the penultimate ones being crimson. 



A rarer corymbose member of the genus Madrepora is delineated by Fig. 3 of Chromo 

 plate IX. Its corallum somewhat resembles that of the species last described, but possesses 

 larger branchlets, with more excert corallites and larger calicinal orifices. It is chiefly remarkable 

 for its brilliant colour, both the corallum and the extended polyps being a rich violet hue 

 throughout. This species, w.ihich is seldom uncovered by the tide, has been obtained by the 

 author on the Warrior reef, in Torres Strait, and in the neighbourhood of the Lark Passage, a 

 little north of Cooktown. The coral proving to be a species new to science, Mr. Brook has 

 paid the author the compliment of associating it with his name. A photographic represen- 

 tation of a complete bouquet-shaped corallum of this fine species is reproduced in Fig. 21 of 

 Plate I. An exceedingly handsome and more robust corymbiform type of the genus Madrepora, 

 commonly distributed throughout the Barrier district, has been associated by Mr. Brook with 



