38 PERCY SLADEN TRUST EXPEDITION 



ii. Corallites usually large and oblique. Costal and perithecal spines 

 conspicuously high, their bases often fused to form perithecal ridges ; more than twelve 

 septa {i.e. a varying number of tertiaries also) meeting columella ... Echinopora. 



b. Perithecal spines absent. 



i. Peritheca highly vesicular; corallites usually projecting far above peritheca 

 with markedly exsert septa ; inter-corallite furrows absent ... ... Galaxea. 



ii. Peritheca dense ; corallites level or slightly projecting, with septa little 

 exsert; polygonal inter-corallite furrows present... ... ... Leptastrea. 



B. Corallite- walls perforate ... ... ... ... Diploastrea. 



II. Corallites usually formed by fission, sometimes by budding ; septa without 

 cyclical arrangement, number meeting columella indefinite ... Group II. 



A. Corallite-walls usually separated by perithecal regions of varying thickness ; 

 septa not of equal width at calicular margins ; an alternating cycle of rudimentary septa 

 absent or present ... ... ... ... ... ... Favia. 



B. Corallite-walls fused ; septa of equal width at calicular margins ; an alter- 

 nating cycle of rudimentary septa present ... .. ... Goniastrea. 



IV. SYSTEMATIC. GEOUP I. 



Genus Cyphastrea, Klunzinger. 



1816. Astrea (pars), Lamarck, Hist. anim. sans vert., ii, p. 257. 



1834. Explanaria (pars), Ehrenberg, Korall. roth. Meer., p. 82. 



1834. Favia (pars), Ehrenberg, Korall. roth. Meer., p. 93. 



1848. Astrcea, subgen. Orhicella (pars), Dana, Expl. exp. Zooph., p. 205. 



1848. Cyphastrea, Milne Edwards and Haime, Compt. rend. I'Acad. Sci., xxvii, p. 494. 



1848. Solenastrea, Milne Edwards and Haime, Cbmpt. rend. I'Acad. Sci., xxvii, p. 494. 



1857. Cyphastrma (pars), Milne Edwards and Haime, Hist. nat. CoralL, ii, p. 484. 



1857. Solenastrcea, Milne Edwards and Haime, Hist. nat. CoralL, ii, p. 495. 



1879. Gyphastrcea, Klunzinger, Korall. Roth. Meer., p. 50. 



1884. Solenastrcea and subgen. Gyphastrcea, Duncan, Journ. Linn. Soc. London, Zool., xviii, p. 107. 



1886. Gyphastrcea, Quelch, Reef Corals, Challenger Reports, ZooL, xvi, pt. xlvi, p. 106. 



1889. Gyphastrcea, Ortmanii, Steinkorall. Sud. Ceylons, Zool. Jahrb., iv, p. 529. 



1899. Gyphastrcea, Gardiner, Proc. Zool. Soc. London, p. 761. 



1904. Gyphastrcea, Gardiner, Fauna Geogr. Maldives and Laccadives, ii, p. 778. 



Corallum. Growth-form variable, mainly incrusting, following any irregularities on 

 surface of attachment, often raised into hillocks, sometimes rounded off and free, usually 

 bored into by various marine animals. Peritheca with dissepiments varying considerably 

 in thickness, spines present or absent. Corallites circular, touching or to 4 mm. apart, 

 level with general surface or to 2 mm. high. Calicos to 2 '5 mm. in diameter. Three 

 orders of septa : a primary entocoelic, a secondary entoccelic and a tertiary entocoelic, 

 consisting of 6, 6 and 12 septa, sometimes fewer. Tertiaries very narrow, costae present 

 or sunk in peritheca. Columella formed of trabeculiB from septal margins. 



In colonies with uneven surface, corallites in valleys almost touching one another and 

 hardly projecting, but septa more exsert than on hillocks. 



