58 MADREPORARIA. 



26. Goniopora Great Barrier Reef (12)12. (PI. III. figs. 7 and 8.) 



[Warrior Reef, " extreme low water," coll. Saville-Kent ; British Museum, 

 and Australian Museum, Sydney.] 



Goniopora frutkosa, Saville-Kent, Rec. Austn. Museum, vol. i. (1891) p. 123, pi. xv. figs. 1-4 ; 



pi. xvi. fig. 1. 

 Rhodarcea frutkosa, Saville-Kent, ' The Great Barrier Reef,' 1892, p. 187. 



Description. — Corallum appears to have been primarily thin and encrusting, but the edges 

 tend to run out into tongues, from the surface of which angular knobs arise, which flatten and 

 divide. In this way low branching tufts may be formed, the terminals of which are about 

 1 cm. long and 1 cm. thick, angular, and rather closely packed. The chief stems are also thin, 

 short, and often flattened. The living layer is 4-5 cm. deep. 



The calicles on the more evenly encrusting portions (see PL III. fig. 8) are nearly sub- 

 circular, open and shallow, with visible flat floors, variable in size, 2 mm. being the largest. 

 Walls, a close not conspicuous reticulum, on their tops and margins the septal stria; are usually 

 very marked. These latter descend vertically to the floor, which consists of a very large colu- 

 mellar tangle, separated from the wall by great numbers of very small interseptal loculi. The 

 irregular frosted twisted granules, which represent the pali, tend to form a clear circular ring 

 rising up in the centre of the columellar tangle, within which ring the skeleton may be either 

 nearly solid, or so light as to suggest a central fossa. On the rising knobs the skeletal 

 elements are light and reticular, and the septal elements tend to disappear in the open 

 reticulum. 



On the tuft formations the calicles differ considerably from the above description (see 

 PI. III. fig. 7).* They are mostly drawn out of the shape and are much shallower. The septa 

 again appear mainly on the tops and at the margins of the walls, but the latter have lost the 

 symmetry of the septal striaj, and consist of an irregular, rather dense, flaky reticulum. The 

 columellar tangle is large, and forms a floor to the open shallow calicles, but the symmetrical 

 ring of pali only appears in calicles which are less drawn out of shape. The same variation 

 as described for the more normal calicles is again seen within this central ring. The skeletal 

 elements at the terminals of the tuft-formation though open are stout and not especially friable. 



The3e specimens are very instructive. There is (a) an encrusting specimen which has 

 sent out one long thick tongue, the upper face of which carries a constricted knob as if it were 

 the continuation of the tongue. The calicles on this specimen are of the same type as are those 

 on G. Great Barrier Reef 1, which was also encrusting, and sent out tongues which curled round 

 to form knobs (cf. PI. III. fig. 8 and PI. II. fig. 1). The same general change of character takes 

 place in both cases between the calicles on the encrusting parts and on the knobs. 



In the present case the specimen (a) might easily have been separated from the tuft (b) 

 under a new heading, but the characters of the calicles can be seen to be essentially identical. 



* The figure has been accidentally inverted 



