CORALS FROM MURRAY, COCOS-KEELING, AND FANNING ISLANDS. 183 



of the corallum; (3) the form of the radial corallites; (4) the septal characters 

 are according to the same plan. The differences are as follows: (1) the branches 

 of No. 2 are more slender; (2) the axial corallites smaller and less exsert; (3) the 

 radial corallites are smaller and more uniform in size; (4) the walls of the radial 

 corallites are less dense and somewhat rougher. Without large suites of complete 

 coralla on which variation may be studied, it is not possible to evaluate the differ- 

 ences. The appearance is that the two sets of fragments represent variants of one 



species. 



Habitat, etc., Cocos-Keeling Islands.— Dr. Wood Jones says regarding the 



species: 



"Flourishes upon the barrier flats and is able to withstand a considerable degree of rough 

 water. It is easily killed in sedimentary pools. The colonies form dense branching tufts, 

 and have a very characteristic purple coloration of the terminal zooids." 



Distribution. — Red Sea; Indian Ocean; Great Barrier Reef; Tongatabu; Samoa. 

 Acropora (Rhabdocyathus) murrayensis, new species. 

 Plate 82, figures I, la, lb, specimen from Murray Island. Also plate 12, figure 5, of Dr. Mayer's article. 



The following is a description of the type specimen of this species: 



Corallum of subconical growth-form; that is, there is a central stem from which 

 branches radiate outward on all sides and attain nearly the same length at any level, but 

 the length decreases uniformly from summit to base. Height of specimen, 131 mm.; 

 Q7 mm "below summit, diameter 60 by 76 mm.; 13 mm. below summit, diameter about 

 30 mm Branch near base, maximum length 47.5 mm.; diameter 01 proximal end, 8 mm.; 

 axial corallite, diameter 3.25 mm.; exsert 1.5 mm. Short branch near apex, length 12 mm.; 

 diameter of base, 5 mm.; axial corallites, diameter 3.4 mm., exsert 1.4 mm. Branches 

 simple or give off from 1 to 9 branchlets; some of the larger branchlets have secondary 

 branchlets. Distance between axial corallites of a series of branches in a vertical plane, 

 from 12. ■; to 17.5 mm.; in a horizontal plane, from 8 to 21 mm. 



Axial corallite of main stem, diameter 3.75 mm.; exsert slightly less than 1 mm. 

 Walls thick- outer edge rounded; texture closely reticular, with interspaces of less area 

 than the solid structures. Primary septa well developed, equal, not meeting in the 

 axis- secondary septa distinct but small. The axial corallites of the branches and branchlets 

 similar to the axial corallite of the main stem but slightly less in diameter and slightly more 

 exsert and in some the directive septa are more prominent than the other primaries. 



The radial corallites are prominent to within between 5 and 6 mm. from the branch 

 tips No immersed corallites except near base of main stem. The protuberant corallites 

 occur in fairly definite spirals and are of two kinds, proliferous and non-proliferous. 1 he 

 former are tubular, but with a somewhat better developed outer than inner wall; diameter 

 very nearly 3 mm., length from 3.5 mm. to that of short branchlets, 12 mm. or more. I he 

 other radial corallites are short appressed tubular; the outer wall makes an angle of about 

 ±c° with the branch surface; plane of aperture about perpendicular to the branch surface. 

 Leneth ix to 3.5 mm., diameter 2.5 to 2.75 mm. The outer wall is thick and except very 

 near the branch ends is rounded; outer surface closely granulate The inner wall is fused 

 to the branch surface. Apertures broadly elliptical, more or less labellate Primary septa 

 distinct the directives the more prominent; secondaries small, but usually recognizable. 

 Low down on the branches the corallites become less prominent; on the base ot the main 

 branch they are mostly subimmersed; the septa in the calices of such corallites are con- 

 spicuously well developed in two cycles. 



Ccenenchyma closely granulate, becoming dense; no perceptible costules. 



Stations, Murray Island.— Southeast reef, line I : 



1,600 feet from shore; depth, 10 inches; bottom hard, rocky. 

 1,630 feet from shore; depth, 16 inches; bottom hard, rocky. 



Distribution.— Murray Island. 



It seems to me that Brook placed this species under A. rosaria (Dana) tor he 

 says of the latter, "Corallum very dense, surface and wall closely and finely echinu- 



