112 PERCY SLADEN TRUST EXPEDITION 



from Aldabra and Seychelles (PL 27, figs. 1 and 2) constitute an intermediate series 

 between Gardiner's example from Minikoi and the thin forms from Salomon. The latter 

 specimens show some resemblance to F. bertholleti owing to the thinness of their walls and 

 septa and the comparative shortness of their septal teeth ; hence their place in F. hem- 

 prichii is doubtful. 



Of the five specimens in the Berlin Museum named Astrcea dipsacea, Ehrb., four 

 have been later referred to Acanthastrcea hirsuta var. inicrostoma by Klunzinger — one, 

 measuring 19x14x10 cm. is figured — and the fifth to var. megalostoma. The former, 

 though possessing the thickened character of the latter, have smaller corallites and fewer 

 septa ; I am therefore led to think that they, like the similarly named example of Gardiner's, 

 form an extreme case of skeletal variation in the present species. Klunzinger 's figured 

 type of var. megalostoma is not in the Berlin Museum. 



Milne Edwards and Haime's type of Prionastrcea hem^prichi is a small incrusting 

 specimen (11x9 cm.) from the Red Sea; it undoubtedly is identical with both Ehrenberg's 

 and Klunzinger's types. The spines on the exsert septal ends are even longer than in 

 Klunzinger 's example, the corallite -walls are ridged, 2 — 4 of the principal septa are 

 thicker and broader, but to a less extent than in Gardiner's type of Favia adduensis, 

 and the corallites have a tendency to meander as in my examples. In the Paris Museum 

 there is also a large specimen from Koseir named P^'ionastrcea spinosa. 



Localities. Seychelles (5). Minikoi (l). Chagos, Salomon (5, thinner than the rest). 

 Previously known only from the Red Sea. 



20. Favia favosa (Ellis and Solander). (PL 28, fig. 2.) 



1786. Madrepora favosa, Ellis and Solander, Nat. Hist. Zooph., p. 167, pi. 50, fig. 1. 



1797. Madrepora favosa (pars), Esper, Forts. Pflanz., p. 34, pi. 45a, fig. 1 (copy of Ellis and Solander's figure). 



1830. Dipsastrea favosa, Blainville, Diet. Sci. Nat., Ix, p. 338; Manuel d'actinol, p. 373. 



1850. Frionastrea magnistellata, Milne Edwards and Haime, Ann. Soi. Nat., Zool., 3"= ser., xii, p. 129. 



1850. Frionastrea favosa, Milne Edwards and Haime, Ann. Sci. Nat., Zool., 3'' ser., xii, p. 132. 



1857. Acanthastrcea bowerbanki, Milne Edwards and Haime, Hist. Nat. CoralL, ii, p. 503, pi. D6, fig. 1. 



1857. Prionastrcea magnistellata, Milne Edwards and Haime, Hist. Nat. Corall., ii, p. 516. 



1857. Frionastrcea favosa, Milne Edwards and Haime, Hist. Nat. Corall., ii, p. 520. 



I refer to this species a single massive convex specimen from Red Sea measuring 

 ] 9 x 17 X 14*5 cm. which closely resembles Ellis and Solander's figure of Madrepora favosa 

 (the type itself is missing from the Glasgow Museum). It has polygonal corallites, the 

 calices of more or less uniform width along their entire height with diameters up to 

 20 and 14 mm. (average 18 and 13 mm.) and depth up to 11 or 12 mm. The inter- 

 calicinal walls are flat, being about 3 mm. The total number of septa vary up to 50 

 (average about 42) ; of these 16 — 18 septa meet the columella, their upjjer two-thirds 

 being narrow and vertical while their lower thirds are broader and simulate a pali-crown. 

 The septa have rough sides, short teeth (about 10) on their edges, and are exsert for 

 1 or l"5mm. The exsert ends are usually arched, those of neighbouring corallites either 

 alternating or meeting, and are usually connected along the middle of the walls by a 

 thin ridge. Owing to the arched condition of the exsert ends, the walls appear grooved 

 above. The columella is formed by loosely interlacing septal trabeculse and is ^ — ^ the 

 width of the calyx. New corallites are formed by unequal fission. 



