56 PERCY SLADEN TRUST EXPEDITION 



is usually somewhat bent. In the endoderm of the oral-disc algee are not massed 

 together, hence its vacuolated condition better seen; the nuclei are not arranged along 

 its periphery as in the previous two species; the circular layer of muscle-fibres is 

 distinctly visible. The mesenterial endoderm appears somewhat diffuse and transparent, 

 with fewer algse than in the two previous species, and is not specially thickened into 

 a pad behind the filaments. Gonads v^ere not present in any of the polyps examined 



Polyps examined, three; from a specimen from Dongonab, Red Sea. 



B. Corallum. In the Paris Museum there are three specimens referred by Lamarck 

 to Explanaria geTnmacea, later re-described by Milne Edwards and Haime as Echinopora 

 gemmacea; one (9x9 cm.) of these from the Red Sea is identical with my types of 

 the present species; another (10x9 cm.) from the Indian Ocean is a concavo-convex 

 specimen, with a short hump and with the corallites projecting obliquely, in every respect 

 resembling specimen no. 12 on p. 57 ; the third (8 x 7'5 cm.) from the same locality is 

 a flat, somewhat worn-out example. Seven excellent specimens have been assigned by 

 Milne Edwards and Haime to E. ehrenbergi; two of these from Seychelles (30x21 cm. 

 and 25 x 23 cm.) have typical corallites on the flat regions, but on the frequently branching 

 hillocks corallites and peritheca are much coarser, as in specimen no. 10 on p. 57 ; a specimen 

 (19'5 x 11"5 cm.) from Red Sea, with humps, has obliquely projecting corallites and a few 

 short perithecal spines resembling no. 12 ; another specimen (19 X 18 cm.) from the same 

 locality has an incrusting corallum rising into branching hillocks, the flat regions 

 resembling no. 13, while the hillocks are identical with Stephanocora hemprichi forma 

 fruticulosa of Ehrenberg; the remaining three specimens from Red Sea have the 

 fruticulosa, facies, but the calices are somewhat smaller, 4 — 5 mm. in diameter. Milne 

 Edwards and Haime's original of ^. solidior (22 x 19 cm., PL 16, fig. 5) has an incrusting 

 corallum raised into short humps, being identical with my typical specimens of E. 

 gemmacea; the average diameter of its calices is about 5 "5 mm.: perithecal spines are 

 slender and septa thin in calices. There are no specimens at present in the Paris 

 Museum named E. hemprichi, but doubtless the species comes under E. gemmacea. 



I have carefully examined the five large specimens from Red Sea, for which Milne 

 Edwards and Haime constituted a new species Heliastrcea forskcelana, and have no 

 hesitation in referring them to E. gemmacea. 



In the Berlin Museum are three specimens referred by Klunzinger to E. ehrenbergi ; 

 two of these were Ehrenberg's originals of Stephanocora hemprichi. Klunzinger has 

 figured the smaller (PI. VI, fig. 7); the larger measures 25 x 16 cm. ; the remaining one is 

 a small edge specimen, 9x6 cm , which also has been figured (PI. VI, fig. 9). Ehrenberg's 

 type of Stephanocora hemprichi forma fruticulosa is a large specimen with a dendroid 

 mode of growth, inconspicuous perithecal and costal spines, costae continuous from 

 corallite to corallite over the perithecal regions, and calices somewhat larger. Klunzinger 

 separated it into a new species E. fruticulosa, but it is only a skeletal variety of the 

 present species, as is evident from some of Milne Edwards and Haime's examples 

 of E. ehrenbergi, on which fi'uticulosa hillocks are seen on typical coralla (see PI. 16, 

 fig. 5). Klunzinger's type (20"5 X 12-5 cm.) of E. concamerata — formerly Ehrenberg's 

 example of Explanaria hemprichi — has some of the characters of E. lamellosa, Esper, 



