184 PAPERS FROM THE DEPARTMENT OF MARINE BIOLOGY. 



late."' Until I had closely studied the specimen just described and had compared 

 it with the type of A. rosaria, I thought they belonged to the same species, but 

 A. murrayensis has a much denser texture and it has not the costules so conspicuous 

 on both the axial and radial corallites m A. rosaria. A. murrayensis is very close 

 to A. squarrosa (Ehr.), of which it may be only a growth-form. 



Acropora (Rhabdocyathus) squarrosa (Ehrenberg). 



Plate 83, figures 2, la, 2b, specimen from Murray Island. 



1906. Acropora squarrosa von Marenzeller, Denksch. k. k. Akad. Wlss. Wien, vol. 80, p. 46, plate 14, 

 figs. 36-39 (all figures). 



Description of specimen from Murray Island: 



Corallum cespitose, rising as a number of separate branches from an incrusting base. 

 Height about 12.5 cm. Branches about 60 mm. long; basal diameter about 10 mm. There 

 are irregularly distributed lateral branchlets and proliferous corallites, but some branches 

 show subequal branchlets at the same level. A brancblet 22 mm. long may have a basal 

 diameter of only 3.5 mm. 



Axial corallites, 2.5 to 3 mm. in diameter, exsert i to 2.5 mm.; walls thick, reticulate, 

 become compact, externally granulate, with perceptible costules; aperture about i mm. 

 in diameter; septa in 2 distinct cycles, the directives somewhat the longer, the secondaries 

 shorter than the primaries. 



Radial corallites, mostly appressed tubiform, or tubiform and proliferous near the 

 branch terminals; near the branch bases they are mostly immersed. The proliferous coral- 

 lites range in size from a length of 4 mm. and a diameter of 2.25 mm. to well-developed 

 branchlets. The usual protuberant corallites are about 3 mm. long and 2 mm. in diameter. 

 The outer wall rises at an angle of about 45°; plane of the aperture nearly perpendicular to 

 surface of branch. Outer wall thicker than the inner, becomes dense, upper edge slightly 

 rounded; surface echinulate, with some indefinite costulations. Inner wall ranges in con- 

 dition from that of fusion to side of the branch to that found in tubular corallites. Aper- 

 tures broadly elliptical or oval, labellate or subnariform. 



Primary septa distinct, the upper directive often the more prominent; secondaries 

 often well developed but small. Frequently the septa show the following arrangement: 

 the upper (dorsal) and lower (ventral) directives mark the plane of symmetry; both of these 

 are free from lateral septa, but the two primary and the two secondary septa distal of the 

 upper (dorsal) directive on each side of the plane of symmetry may form four pairs, while 

 the secondaries, one on each side, next the ventral directive remain free. The septal 

 grouping is similar to that of those species oi Porites in which the inner ends of the members 

 of the triplet are all free, but with two lateral pairs on each side of the plane of symmetry. 



Coenenchyma firmly but roughly echinulate, decidedly dense. 



Station, Murray Island: — Southeast reef, line I, 1,400 feet from shore; depth 

 14 inches; bottom hard, rocky. 



This differs from A. murrayensis by its growth-form and its smaller corallites. 

 The presence of distmct lateral pairs of septa is noteworthy as indicating relation- 

 ship with the Poritidae. A. glauca (Brook) is very close to, if not a synonym of, 

 this species. 



Distribution. — Red Sea; Australia. 



Acropora (Rhabdocyathus) rosaria (Dana). 

 Plate 82, figures 2, 2a, 2i, Dana's type of the species. 

 1846. Madrepora rosaria Dana, U. S. Expl. Exped., Zoopli., p. 465, plate 36, fig. 3. 



Notes on the texture and ornamentation of the corallite walls of this species 

 are given in the remarks following the description of ^. murrayensis. The figures 

 (plate 82, figs. 2, 2a, 2b) are intended to show the growth-form, the septal and 



'Cat. Genus Madrepora, p. 179. 



