152 MADREPORARIA. 



SUPPLEMENT TO GROUP II. (Vol. IV. p. 48.) 

 Australian Forms. 



159. Goniopora Great Barrier Reef (i6)13. (G. Queenslandice tertiadecima.) 



(PI. VIII. fig. 4.) 



[Moreton Bay, coll. W. Saville-Kent ; British Museum.] 



Description. — The corallum is a detached, massive, bean-shaped nodule, which rested, in 

 part at least, upon low prominences of its surface, the tips of which seem to have suffered from 

 contact with the substratum. Between these prominences the surface is smooth. 



The calicles are nearly flush with the surface, being only shallow depressions, subcircular, 

 and varying from 1 to 2 mm. in diameter. The walls are only the slight ridges between the 

 depressions and not raised as steep ramparts. They are everywhere obviously composed of 

 the thick, peripheral ends of the septa, but occasionally show a tendency to be reticular. 

 The septa, about twenty, with granular and frosted edges, taper towards the centre, and are 

 usually symmetrically arranged on each side of the directive plane. The missing parts of the 

 typical formula are apparently always those near the directives. The columellar tangle is 

 seldom visible at the surface, being replaced by irregular groups of minute septal teeth or 

 granules, which get smaller and smaller as the septa taper inwards. Occasionally a few of the 

 granules near the centre show traces of beginning to rise as pali. 



This Goniopora occurs further south than any of the other known representatives of the 

 genus. It seems to have been lying on coarse sand, some of which was found embedded in 

 the small knobs on which the specimen rested. 



The habit of the specimen instantly recalls that of certain Porites and Montipores which 

 also lie free on a sandy bottom near the Amirantes Islands in the Indian Ocean. In all of 

 them the calicles are more or less flush with the surface, with the same close skeleton, the 

 same kind of frosted granulations, and the same yellowish-sandy colour. Further, detaclied 

 fragments of other Porites sometimes acquire the same kind of skeleton and colour, compare 

 Vol. V. p. 80 (No. 1904. 10. 17. 37). It is difiBcult tlien to avoid the conclusion that the 

 so-called specific characters of this coral are due to its environment. We do not yet know 

 whether it is an accidental growth, derived peiliaps by fracture from some fixed stock, or 

 whether some representative of the genus has acquired tlie habit of living in this way, its 

 parental polyp having perhaps settled upon some small loose pebble or shell which is gradually 

 coated over. 



The specimen is further interesting because patches of it are being killed by an alga 

 which hoUows out the skeleton. In the case of G. Great Barrier Beef 6, p. 53, Vol. IV., the 

 alga was mainly confined to the walls, wliich in that coral are high, but here it is in both septa 

 and walls ; the former being almost as near the surface as the latter. 



o Zool. Dept. 92. 12. 1. 315. 



