144 Zoological Society : — 



This coral is very neat and symmetrical, and can hardly be con- 

 founded with any other species. 



2. Flabellum mobile. 



Much compressed throughout, elongated. Borders rather con- 

 cave, with four or five root-like appendages more or less distant from 

 the base, but closely united throughout their length to the lower 

 half of the coral. These appendages spring from and are continuous 

 with the transverse epithecal ridges which mark the successive 

 periods of increase in the coral, and, although now intimately united 

 to the main stem, are evidently of extraneous growth, corresponding 

 in origin and nature with the ordinary form of spines, but taking a 

 downward direction to increase the basal area. Upper margin of 

 the coral slightly arched. Cell very deep and narrow. Margin of 

 lamellae entire, and gradually curving from apex to base, at which 

 point opposite series of the larger plates almost unite. No colu- 

 mella perceptible. Four principal lamellae in half an inch. 



The two specimens which have furnished the above description 

 are of different ages. The smaller and more perfect example is at- 

 tached to the upper margin of the flat side of the larger one, and has 

 grown in nearly the same vertical direction. It measures 2 inches 

 6 lines in height, and 1 inch 10 lines in greatest breadth. The older 

 example is 2 inches 6 lines in the long diameter, and 1 inch 3 lines 

 in the short. The base of this specimen is imperfect ; so that the 

 original length of the coral cannot be certainly ascertained. 



This species is intermediate between the genera Flabellum and 

 Rhisotrochus, having the usual compressed shape of the former, with 

 a partial development of the radiciform appendages of the latter re- 

 markable genus. The peculiar situation of the smaller specimen is 

 perhaps worthy of notice, as being one in which the supplemental 

 props are especially useful in aiding the attenuated base to support 

 the long and heavy coral. A similar tendency to parasitic growth, 

 or rather adhesion to another individual of its own species, may be 

 observed in Milne-Edwards' s figure of the type -specimen of Rhizo- 

 trochus*. The species now under consideration should, I think, be 

 placed in the genus Flabellum, although differing in some of its cha- 

 racters from most of the typical forms ; and as it is the largest mem- 

 ber of the genus, I propose to call it nobile. 



The precise habitat of this coral is unknown. It was brought to 

 this country by the late Sir Everard Home ; and as that gentleman's 

 collections were principally made in the neighbourhood of Australia 

 and New Zealand, these corals were probably obtained from the same 

 part of the world. 



The specimens are now in the Museum of the Royal College of 

 Surgeons of England. 



* Milne-Edwards et J. Haime, Ann. des Sc. Nat. 3 e ser. t. ix. p. 282, pi. 8. f. 16, 

 1848. 



