170 REf'KXT MADKEPOKARIA OF THE HAWAIIAN ISLANDS AND LAYSAN. 



vertical triil)cciila. fcrmiiiatiny in a palus. a second vertical trabecula ending on the 

 septal margin in a septal granule, i)eyond the septal trabecula is a vertical wall 

 trabecula. 



Second. Calic(>s in which there are two or more granules between the palus and 

 the apparent wall, with a zone of .s.vnajjticula next the latter. 



Bernard considers that the peripheral ring of .synapticula represents the wall, 

 while the portions of the septa out.sid(>s this ring are in reality costa?. In his diagrams 

 the tral)ccula' are represented as vertical. 



From a study of the series of specimens referred to Porite« co>/ij>ressa^ and its 

 various forma', and of P. dy,rdi'?i/\ I became convinced that the septal trabecule of 

 Parltix are not vertical, but inclined inward, usually at so very slight an angle that 

 unless the longitudinal sections of the corallites extend over considerable lengths the 

 trabecuhv ajipear vertical and parallel. Pm'itcs diumleni, of the forms studied, shows 

 most clearlv that its septa are composed of inwardly inclined trabecula? (see p. lf>3, 

 Plate LXXVIll, iig. 3, and Plate LXXIX, tigs. 1, It). 



The wall trabecula in these species is constantly vertical. The number of septal 

 granules therefore varies, and is a function of the angle of inclination of the septal 

 trabecuhv. The septal structure of the Poritids is therefore entirely homologous 

 with that of other Madreporaria, in which the line of trabecular divergence corre- 

 sponds in position with the wall. In those species that I have studied the portion of 

 the septum exterior of the wall is suppressed, while the inner portion is developed. 

 It is pro))able that trabecule diverging outwardly from the wall are developed in 

 the coenenchymatous forms. 



The septa of Par'de^ are therefore structurally very similar to those of the com- 

 pound, perforate Fungids. The recognition by Duerden and Bernard of the bilat- 

 erality of the Poritid calices, and the discovery by Bernard of the palar formula^, 

 mai'ked great advances in our knowledge of this group of corals. The clear 

 recognition of the essential similarity of their septal structure to that of other 

 Madreporaria may render additional aid in uni-aveling their systematic affinities. 



The genus Porltex is richly represented in the Hawaiian waters. Judging from 

 Bernard's Porites of the Indo-Pacilic Region, only the Great Barrier Keef of 

 Austi'alia has furnished a comparably great number of forms. 



Professor Dana, in his Zoophytes of the Wilkes Exploring Expedition, described 

 from there /'. inordu,i\ P. mordax var. clongata., P. coinprcssa, and P. lohata. 

 Professor Verri 11, in 1864, in his List of C<jrals and Polyps Sent in Exchange by the 

 Museum of Comparative Zoology, added another species under the name of Synarxa 

 ■irregularis. Quelch, in his Report on the Reef Corals of the Challenger Expedition, 

 1886, described P. lulhosa from the reefs of Honolulu; he identified one Hawaiian 

 species with /*. lichen. Dana, from the Fiji Islands, and another with a .species from 

 the Riu Kiu Islands, /*. tenuif: Verrill. These identifications of Quelch are erroneous. 

 Professor Studer, in his Madreporarier von Samoa, den Sandwich-Inseln und Laysan, 

 1901, added P. r/uelehi, P. Innuginom, J', dismideit, and /'. xchauinslandi. Nine 

 species and one variety of Porites have been described and two extraneous species 

 have been identified from the Hawaiian Islands (including Laysan). 



