CORALS FROM MURRAY, COCOS-KEELING, AND FANNING ISLANDS. 87 



Station, Murray Island. — Southeast reef, line I, Lithothamnion ridge, 1,756 

 feet from shore; hard, smooth, waterworn, rock bottom with shallow, crevice-like 

 tide pools; water about 3 inches deep at low tide. 



Distribution. — Torres Strait; Kermadec Islands; eastward to the Paumotus. 



Genus CYPHASTREA Milne Edwards and Haime. 

 1848. Cyphastrea Milne Edwards and Haime, Acad. Sci., Comptes rend., vol. 27, p. 494. 



Type species: Astrea microphthalma Lamarck. 



Matthai has recently revised the species of this genus, 1 but as he has made no 

 key to the species, nor has he otherwise clearly indicated their differential characters, 

 I have found it convenient, in order to use his work, to prepare a synoptic table, 

 which is here presented: 



Synopsis of species of Cyphastrea described by Matthai. 



Septa, 3d cycle incomplete. 



Ten usually meet the columella. 



Corralites not projecting or only up to 0.75 mm.; exotheca dense I. C. microphthama. 



Septa in 3 cycles. 



Twelve usually meet the columella. 



Corallites may project up to 2 mm.; secondary costx thinner than the primary; 



exothecal vesicles thin 2. C. serailia. 



Corallites may project up to 1 mm.; secondary and primary septa equally thin; 



exothecal vesicles thicker than in 2 3. C. chalcidicum. 



Corallites not projecting; exothecal vesicles thin, blistery 4. C. suvadivce. 



Six septa meet the columella. 



Corallites project up to 0.75 mm.; exotheca dense 5. C. gardineri. 



An inspection of this table shows that C. serailia and C. chalcidicum are very 

 similar. In addition to the characters given there, Matthai says regarding the 

 latter: 



"Calices usually about 2 mm. in diameter, deeper than in the last species [C. serailia], 

 clearly visible owing to comparative thinness and smoothness of septa. Septa more exsert 

 than in C. serailia, * * * " 



Professor Stanley Gardiner has sent to the U. S. National Museum a good 

 specimen of C. chalcidicum from Goidu, Maldives, labeled by Mr. Matthai, and 

 there are other specimens of it, as well as many specimens of C. serailia, in the 

 U. S. National Museum. The corallites of C. chalcidicum usually project per- 

 pendicularly beyond the exotheca, and the outer ends of the primary and secondary 

 septa terminate in relatively prominent costae, while the costae corresponding to 

 the tertiary septa are small or obsolete. (See Matthai, op. cit., pi. 12, fig. 3.) 

 In C. serailia the tertiary costae are usually distinct and well developed, although 

 costae corresponding to the primary and secondary septa are usually less prominent 

 than in C. chalcidicum (see Matthai, op. cit., pi. II, figs. 2 and 4). Although 

 intergrades between these forms may be found, the probability is in favor of their 

 being different species. 



With regard to Cyphastrea ocellina (Dana), which I have redescribed and 

 figured in my paper on the Madreporaria of the Hawaiian Islands and Laysan, 2 

 and which Matthai doubtfully refers to the synonymy of C. chalcidicum, I will 

 say that, in my opinion, it is a valid species. The calices are smaller than in C. 

 chalcidicum, on projecting calices distinct costae correspond to the tertiary septa, 

 and the primary septa are thicker than the secondaries. 



'Trans. Linn. Soc. London, 2d ser., Zool., vol. 17, pp. 38-48, 1914. 



2 U. S. Nat. Mus. Bull. 59, pp. 103-104, plate 25, figures 4-50, plate 26, figure 1, 1907. 



