MATTHAI— RECENT COLONIAL ASTR^ID^ 99 



in addition to closely packed nematocysts I, the larger ones having 40 to 50 turns of the 

 spiral ; sub-terminal batteries number 3 or 4. The stomodseum is laterally compressed 

 with its diameters in the retracted condition measuring 1"25 and '75 mm. ; owing to the 

 radial contraction of the mesenteries some of the ridges are pulled outwards, appearing 

 somewhat concave in transverse section. Small nematocysts I, similar to those in the 

 oral-disc, are present in the stomodseal ridges, in which the mesoglsea is not thickened. In 

 the ectoderm of the oral-disc numerous mucous vacuoles are present; small nematocysts I 

 are fairly frequent, but II are scarce. 



Filaments are present on all the mesenteries ; nematocysts I occur in their straight 

 regions as in the stomodseal ridges, but have fewer coils ; where numerous, nematocysts III 

 are arranged in rows, many with threads partly discharged ; some of type II, with the 

 axes usually bent a little, are also found. Convolutions of the mesenteries are pro- 

 truded into the stomodaeum. The endoderm is, as a rule, much vacuolated; in the 

 oral-disc it is as thick as the ectoderm over it ; in the tentacles it fills their lumina. 

 The gastro-vascular cavity is blocked below the stomodseum owing to the swollen condition 

 of the mesenterial and column-wall endoderm and to the abundance of the mesenterial 

 convolutions. Algae are massed together in the endoderm of the oral-disc and tentacles, 

 scarce in the mesenterial endoderm. Gonads were not present in any of the polyps. 

 Number of polyps examined, five, all from one colony from Dongonab, Eed Sea. 



B. Corallum. Ellis and Solander's figured type of Madrepora ananas is missing 

 from the University Museum, Glasgow, but judging from the figure there is little doubt I 

 am dealing with a specimen similar to theirs. Since Madrepora ananas of Linnseus is, 

 according to Milne Edwards and Haime, a Cyathophyllid = y4cera?/,/arm ananas (Corall. iii, 

 p. 412), Ellis and Solander's specific name may be retained lor the present species. 

 Milne Edwards and Haime's original of Flesiast7'CBa peroni is missing, but their figure 

 resembles my specimen, the only difierence being that in the former the corallites appear 

 to project more. 



Verrill's figure of his species, Plesiastrcea indurata, greatly resembles my type 

 specimen, but his specimens have to be examined before the relationship of his species to 

 the present can be finally settled. 



Localities. Red Sea (l small). Also known from ? Australia (Milne Edwards and 

 Haime), ^Loo Choo Islands (Verrill), ?loc. (Ellis and Solander). 



9. Favia laxa (Klunzinger). (PL 24, figs. 5 and 6 ; 37, fig. 2.) 



1879. Orbicella laxa, Klunzinger, Korall. Roth. Meer., iii, p. 49, pi. 5, fig. 3, pi. 10, figs. 9a and 96 (non 

 Orbicella laxa, Gardiner). 



Oorallum. Massive, tending to be rounded off", sometimes incrusting. Peritheca 

 vesicular, the dissepiments about 75 mm. apart. Corallites circular or laterally com- 

 pressed, projecting about 1 mm., sometimes almost level, with distinct rims, usually about 

 1 — 2 mm. apart, always separated by inter-corallite furrows. Calices 4 — 6 mm. in diameter 

 depth 2 — 3 mm. 



Septa thickening towards walls, usually vertical, with toothed edges, crowded blunt 

 spinules on sides, exsert to "5 or 75 mm., up to 37 in number, average 32 ; of these 



13—2 



