76G J. STANLEY GARDINER. 



XI. Genus Favia. 



Ed. and H., ii. p. 426. Klz., p. 25. Astraea, Gard., p. 747. 



The genus is in many respects a most unsatisfactory one. On the one side it ahnost 

 merges into Coeloria (vide C. astraeiformis, Ed. and H.), and on the other into Gonias- 

 traea. Indeed, many species are in parts at any rate indistinguishable from the hitter, save 

 in microscopical sections. Again, Orbicella approaches close to it in that some of its species 

 show fission moderately freely and some intracalicular gemmation (which may simulate fission) 

 as well as the more regular extracalicular. The presence of a valley or sulcus between the 

 corallites is really no test, and the septa are often continuous in Orbicella between the 

 calices and within the walls. 



The species in the collection are most variable, even more so than those of Orbicella 

 and Prionastraea. Attention may be particularly drawn to F. denticulata, in 16 specimens 

 of which I have attempted to work out the variability, both normal and vegetative, and also 

 to F. hululensis. The species fall naturally into three groups: (a) those with rather 

 rounded calices, sulcus on walls, theca distinct, paliform lobes more or less prominent, and 

 exsert portions of septa generally horizontal ; (6) angular calices, thin walled and no sulcus, 

 marked paliform lobes, exsert parts of septa rounded or rough ; and (c) gyrose calices. No. (a) 

 includes F. cavernosa, denticulata, hululensis and hombroni, a very close series, a gap 

 in size only between the last two, with offshoots in F. affinis and laccadivica. In (6) we 

 have F. halicora and parvimurata, which might almost be placed in Goniastraea, and in 

 (c) F. versipora and adduensis, the former particularly recalling certain Coeloria. 



Distribution. The genus is essentially dominant over all other massive forms on lagoon 

 shoals in Minikoi and throughout the Maldives ; it is also, with the possible exception of 

 Prionastraea, the most abundant in the waters of the outer slope to about \5 f. It is seldom 

 found on the reef-flat, and generally shuns all sandy spots, or where sediment may collect. 

 Its colonies on the lagoon shoals of Minikoi form enormous, overhanging masses, several feet 

 in thickness, often dead in the centre but living on the sides. Numerous boring organisms, 

 particularly Sipunculoids, find a home in its coralla, but seldom distort its surface. Only one 

 specimen was dredged, that of F. adduensis, from 2.5/! Colour of thu living colonies almost 

 invariably some shade of green. 



20. Favia versipora (Ehrb.). 



Favia ehrenbergi = F. versipora (Ehrb.), Klz., p. 29, ill. 5, 7 and 8, and ix. 1 a and /). 

 Favia bertholleti, Ed. and H., p. 431. 



A single specimen from the edge of the reef at Minikoi belongs to Klunzinger's typical 

 form of this species. Its walls are, indeed, more rounded, septa thicker and less numerous 

 (18 to 26), and calices rather smaller, but these appear to me to be vegetative variations. 

 Here and there I find a calice with its septa having relatively long teeth, and this fact, 

 coupled with the number of septa, causes me to consider F. bertholleti to be merely a 

 synonym, as indeed I deem all those suggested by Klunzinger. 



21. Favia adduensis, n. sp. (PI. LXII. fig. 6.) 



Colony massive, or somewhat incrusting. Calices irregular, seldom rounded, angular, 

 elongated, twisted or gyrose, largest 10 by 5 mm., average 6 to 7 by 4 mm., 3 to 4 mm. 



