178 PAPERS FROM THE DEPARTMENT OF MARINE BIOLOGY. 



(1 mm.) aperture. Radial corallites not crowded, usually nariform or tubular, 3 to 4 mm. 

 long and 2 mm. broad, slightly compressed; aperture small, round elliptical or oblique, 

 outer part of wall a little thickened and margin rounded; some of the tubular ones are 

 elongate (7 mm.). Near the base of the branches the corallites are verruciform with a 

 few immersed ones interspersed. Corallum porous above; surface echinulate or spongy- 

 reticulate; wall not striate. ■ , • 



"A specimen from Ceylon described by Ortmann differs from the type in having smaller 

 axial corallites, 3 to 4 mm. diameter and 1 mm. exsert. The species approaches 71/. [Madrepora] 

 klunzingeri closely, and differs chiefly in the form of the radial corallites and in the thickness 

 of the wall. 



"Indian Ocean; Red Sea; Ceylon. 



"a. Ceylon. Haeckel Coll. 92.12.5.7. 



The texture of the Cocos-Keeling specimen is decidedly compact, but this is 

 a recognized adaptation to rough water, and the surface is densely granulate, with 

 secondary minute frosting. In plan the granules show arrangement along more 

 or less definite lines. The septa are strikingly well developed, as is usual in stunted 

 specimens of the genus. Two cycles are persistently present, and in some axial 

 corallites a varying number, up to about 8, of rudimentary tertiaries may be 



detected. 



Habitat, etc., Cocos-Keeling Islands.— Dr. Wood Jones says: "From the extreme 

 rough water of the barrier. The color is usually yellowish; sometimes brown." 



Acropora (Isopora) palifera (Lamarck). 



Plate 78, figures I, la, lb, if, id, Dana's type of Madrepora labrosa; plate 79, figure 1, specimen from Cocos- 

 Keeling Islands; figures 2, 3, 4, 40, 4*, variety a (Brook), from Murray Island. Also plate 13, figure 8, of 

 Dr. Mayer's article. 



1893. Madrepora palifera Brook, Cat. Genus Madrepora, p. 13 1 (with synonymy). 



1893. Madrepora hispida Brook, Cat. Genus Madrepora, p. 133, plate 9, fig. C. 



1907. Isopora hispida Bedot, Madreporaires d'Amboine, p. 262, plate 42, figs. 235-239. 



Dana's type of Madrepora labrosa (see plate 78, all figs.), which Brook referred 

 to the synonymy of Astrea palifera Lamarck, is preserved in the U. S. National 

 Museum, No. 315. Although both Dana and Brook grasped the important char- 

 acters of the species, some of the features need elaboration. The corallites near the 

 branch summits range from 2.75 to 3.5 mm. in diameter; lower down the diameter 

 may be only 1.5 mm., while on the base it may be as little as 1 mm. Upper 

 wall less developed than lower, often absent. Septal pairing often obvious. The 

 radial corallites are crowded in places, especially near the branch terminals, or are 

 considerably separated, 0.5 to 0.75 mm. The lower wall especially shows crowded, 

 flattish, spinulose costules. The ccenenchyma is beset with crowded, more or less 

 twisted spinules which may be arranged in rows. 



Madrepora hispida Brook seems to me to be a form of Acropora palifera with 

 corallites slightly smaller than the average. 



Dr. Mayer collected a good suite of specimens of this species around Murray 

 Island (see plate 79, figs. 2, 3, 4, \a, \b). The radial corallites do not attain so 

 large a size as in the type specimen of A. labrosa, 2.75 mm. being about the maxi- 

 mum diameter, and a larger proportion of them are subtubular. In most specimens 

 the branches are not so plate-like as in A. labrosa (type); but in some they are 

 plate-like. The usual form is Brook's variety a, concerning which he says: 



"The specimens numbered k tow come somewhat intermediate between typical 71/. 

 palifera and 71/. brueggemanni. They have thick branches with broad flat apices, or even 

 sometimes there is only one axial corallite. The radial corallites are irregular, and some 

 are somewhat elongate with a convex outer margin such as occurs in M. brueggemanni 

 var. uncinaia; in other cases the wall is rough and there is an approach to M. hispida." 



