AUSTKALIAN GONIOPOR.E. 53 



20. Goniopora Great Barrier Reef (12)6. (PI. II. figs. 7, 8 ; PI. XI. fig. 12.) 

 [Albany Passage, Northern End of the Great Barrier Reef, coll. Saville-Keut ; British Museum.] 



Description. — Corallum a hemispherical mass capping smaller growths of the same. A 

 thick wrinkled epitheca under each of the edges, whicli in this case were prevented from 

 closely encrusting by the presence of foreign organisms. 



Calicles subcircular, about 3 mm. across, from 1-2 mm. deep, with open ragged margins 

 (that is, not as if neatly punctured). The walls at the toj) are smooth thin lattice, with friable 

 denticulate edges ; but everywhere tend to thicken into an elegant but rather irregular 

 reticulum (see fig. 7). The septal tips do not striate the top of the wall except in lateral 

 calicles (fig. 8). Occasionally instead of septa a row of meshes is conspicuous on the top of 

 the wall when looked at from above. Septal ridges not usually apparent round the mouth of 

 the caUcle except in shallow lateral calicles. The primaries as a row of sharp spines form a 

 conspicuous symmetrical six-rayed star, the teeth turning up to form a compact ring of thin 

 plate-like pali, which in the lateral calicles become very irregular and jagged. Secondaries 

 fairly well developed, sometimes fusing near the centre with the primaries. The tertiaries 

 quite rudimentary, except in the lateral calicles, where traces of the typical formula can be 

 seen in the jagged reticulum formed by the thickened wall and the large columellar tangle. 



This is one of the Gonioporas in which the melting down of the skeletal elements to form 

 a reticulum has just gone far enough to retain a radial symmetry underlying a very beautiful 

 irregularity of texture. It belongs to the group with deep calicles and conspicuous rosettes of 

 pali. The youngest growth composing the stock is about 3 cm. in diameter, and is interesting 

 because the ivalls of its calicles as seen in section are hollowed out by an alga, while the intra- 

 calicular skeleton has been generally spared. It is not easy to see the reason for this 

 differential action, unless it be that the growing tips of the alga were confined to the 

 extreme top edges of the walls and thus raised above the level of the septa.* 



The most recent growth is some 8 cm. in diameter, but seems to have been kept from 

 closely encrusting the earlier growths by the presence of other corals. The rosette of pali in 

 the lateral calicles looks very symmetrical to the naked eye, but under a pocket lens the 

 symmetry disappears. The jagged spiky reticulum is well shown in the figs. 7, 8 (PI. II.), 

 which represent as usual the upper and lower calicles respectively. 



a. Zool. Dept. 92. 12. 1. 149. 



21. Goniopora Great Barrier Reef a2)7- (PL II. fig. 9, and PL III. figs. 1, 2; PI. XII. fig. 1.) 



[Warrior Islands, Torres Strait, colls. W. Saville-Kent and A. C. Haddon ; British Museum.] 



Description. — Corallum forms rounded masses, tlie lower edges closely adhering and 

 bending under. 



* See J. L. Ducrdcn on Boring Alga; in the Bull. Anier. Mus., vol. .\vi. (1902) p. 323. 



