176 THE GREAT BARRIER REEF. 



living aspect of this organ, or, more correctly, its external orifice, with remarkable distinctness, it 

 indicates, with greater clearness, perhaps, than the photographic reproductions previously referred 

 to, the close association of each of the more or less contracted tentacles with the internal edge 

 of a septal element. The distinct enlargement and lighter coloration of the distal terminations 

 of several of these tentacles, is particularly well defined in this figure. 



There are few, if any, of the Mushroom-corals that possess such relatively large tentacles as 

 those of the species just described. It has, moreover, been the remark of a leading authority on 

 corals — Mr. J. D. Dum [Coral and Coral Islands, p. 46) — that in all the species observed by him 

 the tentacles were small and rudimentary. Fiiiigia crassiteiitacidata was, apparently, not represented 

 on those reefs among the Pacific Islands with which Mr. Dana made himself acquainted. So far, 

 nevertheless, as the remaining Barrier Reef varieties are concerned, Mr. Dana's experience can be 

 confirmed. Some half-a-dozen species, in addition to the one already named, were obtained by the 

 author from the Barrier district ; and in all of them the extended tentacles were relatively small 

 and inconspicuous, in many instances presenting the form, only, of small triangular points. One 

 such small-tentacled Fungia, Cycloscris cvclolitcs, is represented in profile by Fig. 16 of No. VI. oi 

 the chromo-lithographic plates. The earlier-stalked, or sessile, young of several of the above- 

 named Mushroom-corals, were collected by the author. As notable among these ma}' be mentioned 

 a species closely allied to Fungia discus, of which an example was collected at Stone Island, 

 Port Denison, in which no fewer than eleven young Fungias, of different ages, were found 

 attached to a single dead parent corallum. A photographic illustration of this remarkable 

 specimen is reproduced in Plate XXIV. 



A gradual transition can be distinctly traced, from the simple Mushroom-corals, to representa- 

 tives of the same family which present as high a degree of aggregated complexity as any of the 

 Astraeacese previously described. Beginning with the simple elongate Fungiae, such as F. ccliinata 

 and aspera, having single oral openings, the first step in the direction of a compound corallum is met 

 with in the genus Cryptabacia, wherein several larger oral openings are developed along the 

 single median longitudinal line, and a limited smaller series along each side. A further advance is 

 accomplished in the two genera Herpetolitha and Polyphyllia, in which, while the corallum is 

 unattached and retains the general contour of an ordinary Fungia corallite, distinct oral areas 

 are developed equally throughout the freely exposed upper surface. Representative types of all of 

 these intermediate genera have been obtained from the reefs of the Great Barrier system, one 

 characteristic form, Herpetolitha talpina, being delineated in Chromo plate VI., Fig. 17. 



Highly specialised compound corals are not wanting in the smaller group now under con- 

 sideration, in which the coralla are attached, and present the massive, encrusting, or foliaceous 

 types of growth, previously enumerated and illustrated in association with the comprehensive 

 section of the Astraeaceae. Encrusting and foliaceous growths, combined, are abundantly typified 

 in the genus, Lophoseris. One species referable to this genus, L. cristata, is so plentiful on the 



