176 PAPERS FROM THE DEPARTMENT OF MARINE BIOLOGY. 



Axial corallites, diameter 3 mm.; exsert, up to 2.5 mm.; septa well developed, primaries 

 almost meeting deep down in the calice, secondaries about half as long as the primaries; 

 wall porous, reticidar, and costulate on the outside, but it becomes considerably compacted 

 by secondary deposit. 



Radial corallites, usually very unequal in size, of three kinds: (a) proliferous, (b) non- 

 proliferous protuberant, and (c) immersed or subimmersed. (<?) The proliferous corallites 

 range up to 8 mm, tall (measured along the lower side) and are 3.5 mm. in diameter; the wall 

 is thick, about 1.25 mm., its inner edge is somewhat excavated, its outer edge rounded in 

 profile, secondarily compacted, but externally costulate, 2 cycles of septa, a false columella 

 present. Corallites of this kind grade into branchlets, which are up to 16 mm. long and 5 

 mm. in diameter at the base. Small, short, labellate, radial corallites occur on the prolifer- 

 ous corallites and the branchlets. {b) 1 he non-proliferous protuberant corallites crowded, 

 labellate, spreading at right angles to the branch, smaller near the branch terminal, larger 

 and more prominent lower down, but still lower near the branch bases, mostly immersed 

 with some large; labellate corallites scattered among them, wider at margin than at base. 

 Near terminals, diameter 1.75 mm., project about 2 mm.; lower down, diameter up to 2.5 

 mm., project up to 2.5 mm. Upper wall poorly developed or absent; lower wall thick, 

 compact, costulate on outer surface, frequently somewhat flattened above. Outer edge 

 more or less rounded in profile. Apertures subcircular in cross-section perpendicular to 

 corallite axis. Lower directive septum prominent; other septa variable in development, 

 usually in two cycles but small in size, rudimentary; however, a false colummella is some- 

 times present deep within the calice. (c) Immersed or subimmersed corallites scattered 

 irregularly between the protuberant ones near the branch terminals; more abundant nearer 

 the base, where they often have 2 well-developed cycles of septa; diameter often only 

 0.5 mm. 



Ccenenchyma costulate, echinulate, decidedly compact. 



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



1,400 feet from shore; depth, 14 inches; bottom hard, rocky. 

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



Distribution. — Great Barrier Reef; Madagascar (Brook). The locality of the 

 type is unknown (see Verrill, op. sup. cit.). 



Professor Verrill has rendered a valuable service in publishing figures of a 

 branchlet from Dana's type. The Australian specimens completely agree with 

 his figures, except that the axial corallites are often, but not always, more exsert. 

 The range of variation of this feature in Dana's type has not been published. 



Acropora (Tylopora) scherzeriana (Bruggemann). 



Plate 75, figures I, 2, 2a, 2b, 3, 30, 4, specimens from Cocos-Keeling Islands. 



1906. Jcropra stheruTiana von Marenzeller, Denksch. k. k. Akad. Wiss. Wien., vol. 80, p. 41, plate 12, 

 figs, 27-31; plate 13, figs. 270, 29fl, 3lfl, 32-35; plate 18, fig. 280 (with synonymy). 



Although von Marenzeller has elaborately described this species and reference 

 may be made to his work, I am publishing figures to show its characters and varia-: 

 tion at Cocos-Keelmg. Besides these specimens, there is in the U. S. National 

 Museum a complete corallum, obtained by Dr. W. L. Abbott in the western Indian 

 Ocean, probably at Aldabra. In 1906' I referred to a species from Mangareva 

 as Acropora afF. J. canaliculata (Klunzinger). A restudy of the species leaves me 

 still m doubt, as the calices are not laterally compressed, as is usual on branches of 

 similar form m A. scherzeriana. 



Habitat, etc., Cocos-Keeling Islands. — "A common barrier species. While living 

 it is yellow; the zooids are pale," according to Dr. Wood Jones. The species is 

 represented by 6 fragments, apparently from 3 colonies. 



'Bull. Mus. Comp. Zool., vol. 50, p. 70, plate 5, figures i, \a, lb. 



