MATTHAI— RECENT COLONIAL ASTR^ID^ 



67 



entoccelic pleats have the same general shape and distribution in both species, broad but 

 constricted at the base, hence appearing knobbed in transverse section, sub-divided usually 

 in G. musicalis, exceptionally in L. roissyana. (6) The mesenterial endoderm is com- 

 paratively thin. (7) The great abundance of algse. 



There are, however, some important differences between the two species, viz. : 

 (1) The general appearance of the colonies is strikingly different in the two cases; in 

 L. roissyana the corallites are close together and almost level with the general surface, in 

 O. musicalis they are wider apart and project above the peritheca. (2) Peritheca dense 

 in L. roissyana, highly vesicular in G. musicalis, the vesicles with thin walls. (3) " Ovoid 

 bodies " are always met Avith in the ectoderm of G. musicalis, their presence being quite 

 diagnostic of Galaxea ; they are absent from L. roissyana. 



The "Challenger" examples of Leptastrea available for examination were all small 

 spirit specimens. Owing to the presence of soft tissues on them, it was impossible to 

 compare them with the continental types, but there is little doubt that most of Quelch's 

 determinations were wrong. 



Distribution. Red Sea, Indian and Pacific Oceans. 



L Leptastrea eoissyana, Milne Edwards and Haime. (PI. 8, figs. 1 — 3 ; 17, fig. 4 ; 



18, fig. 1 ; 19, figs. 1 and 2 ; 37, fig. 4.) 



1850. Leptastrea roissyana, Milne Edwards and Haime, Ann. Sci. Nat., 3'' ser., x, pi. 9, figs. 6 and 6a, and 



xii, p. 120. 

 1857. Leptastrcea roissyana, Milne Edwards and Haime, Hist. Nat. Corall., ii, p. 494. 

 1879. Leptastrcea transversa, Klunzinger, Korall. Roth. Meer., iii, p. 46, pi. 6, fig. 2. 

 1904. Orhicella ehrenhergana (pars), Gardiner, Fauna Geogr. Maldives and Laccadives, p. 776. 



Corallum. Incrusting or massive and convex, rarely rising into humps. Inter- 

 corallite furrows usually distinct, the exsert ends of septa ending at their margins, rarely 

 absent, leaving a sharp ridge over which septa become continuous. Corallites not pro- 

 jecting. Walls about "35 mm. thick, sometimes up to 1 mm. towards edge of corallum. 

 Calices oval or polygonal, widest at their margins, with diameters about 4 and 3 '6 mm., 

 depth to columella 2-6 — 3'6 mm. 



Septa swollen in thecse, thin in calices, with sides smooth, edges entire, in not more 

 than four orders, the first three always complete ; primaries slightly broader than 

 secondaries, both meeting columella, with somewhat oblique margins and exsert to '5 mm. 

 The fourth order often incomplete, usually of about 10 very narrow septa, hence some of 

 the tertiaries exocoelic ; tertiaries often curve towards and meet sides of secondaries near 

 to columella. Columella much compressed laterally, indistinct, primary and secondary 

 septa almost meeting in the centre and forming with the two directive septa a transverse 

 partition across calyx. 



Young corallites formed by budding are seen intercalated among the larger ones. 



Polyps. About 4 mm. in height, with margins somewhat polygonal. Mesenteries in 

 three cycles ; primaries of six couples all meeting the stomodseum ; secondaries of an equal 

 number from half to two-thirds the width of the former ; tertiaries from 2 — 8 couples ; all 

 with filaments in whose coils nematocysts II are common and III rare. Convolutions 

 of mesenteries massed together in inter-mesenteric chambers to some distance below 



9—2 



