90 PERCY SLADEN TRUST EXPEDITION 



non-pleatal region quite thin. (6) Mesenterial endoderm swollen, more in pleatal than in 

 non-pleatal region. (7) Convolutions of mesenteries abundant below stomodaeuija to base 

 of polyps, massed in inter-mesenteric chambers. 



Remarks. A. Polyps. Three polyps have 8 principal couples of mesenteries to each, 

 while the number in another is only 7 ; of these 1 — 5 are incomplete. 17 — 20 secondary 

 couples of mesenteries are present in the tentacular regions of the polyps, of which only 

 10 — 15 extend down to the lower end of the stomodsea. Each of the tentacles has 

 a swollen terminal battery in which incompletely-formed nematocysts II h are interspersed 

 among the closely-arranged nematocysts I, the latter with between 40 and 50 turns of the 

 spiral ; 5 or 6 sub-terminal batteries. The tentacular endoderm is vacuolated and lobu- 

 lated, about the same thickness as the overlying ectoderm, with algse massed together in 

 the region of the terminal battery. 



The stomodseum is laterally compressed, its diameters 1'5 — 2 mm. and '5 — 1 mm. 

 Nematocysts I are of common occurrence in the stomodaeal ridges. The ectoderm of the 

 oral-disc has numerous mucous vacuoles, the endoderm being as thick or thicker, and with 

 closely-packed algas. The mesenterial endoderm is vacuolated and almost transparent, the 

 vacuoles being somewhat oval, and contains few algee. Filaments are present on all 

 the mesenteries; nematocysts I are present in large numbers in their straight regions, 

 while in their coils type III are abundant (unfortunately not properly fixed) ; those 

 of type II are few. The mesenterial endoderm is considerably swollen behind the 

 filaments, up to three times the size of the latter. Below the stomodseum the endoderm 

 of the column-wall is reticulated and quite transparent. Gonads were not present in 

 any of the polyps examined. 



The polyps of this species appear to be more nearly related to F. hululensis than to 

 any other species of Favia. 



Number of polyps examined, eight, 4, 2 and 2, all from Ceylon, also two additional 

 polyps from a doubtful specimen from Minikoi. 



B. Corallum. In the Paris Museum there are three large specimens {H8 x 38 x 12 cm., 

 37 X 29 X 15 cm., 22 X 21 X 12 cm.) from Seychelles, referred by Milne Edwards and Haime 

 to Favia clouei, in which the corallites are oval or irregularly compressed laterally, slightly 

 projecting, coralla light, the perithecal dissepiments about 1"5 mm. apart and the 

 columellae poorly developed (PI. 25, fig- 2), on the whole resembling my Ceylon examples. 

 The same authors have referred three specimens from the Red Sea to Parastrea radiata 

 and later to Favia okeni, the largest of which measures 16x12x8 cm. ; their only differ- 

 ence from Favia clouei is in the larger size of their corallites (PI. 25, fig. 1 ). 



Ehrenberg's type of Favia uva is a large example which Klunzinger later made the 

 type of Favia cavernosa. Marenzeller discovered Klunzinger's mistake in naming this 

 specimen after Forskal's Madrepora cavernosa and correctly pointed out its similarity 

 with Milne Edwards and Haime's types of Favia okeni. Kkmzinger's two examples of 

 Favia tubulifera are essentially similar to Ehrenberg's type, the only difference being that 

 in the former the corallites are not so far apart as in the latter ; my Ceylon specimens are 

 identical with these two species of Klunzinger's. In the Berlin Museum is also a small 

 convex specimen from Ceylon (no. 3729), referred by Ortmann to Favia amplior, 



