86 MADREPORARIA. 



recognisable in the larger calicles, the tertiaries bending sharply round to fuse with the 

 secondaries. The columellar tangle is usually obscured by the thicker granules from the edges 

 of the larger septa, but under these its threads are seen to be thinner, like the edges of the 

 tertiaries. Except for the thickening granules of the large septa there is no rosette formation. 

 In sections the wall is seen as a thin membrane, and the interseptal loculi to be large and 

 conspicuous. Tabula? appear at regular intervals. The coral is massive and heavy. 



The growth-form of this coral immediately recalls the specimens from Fiji, called 

 by Dana " Goniopora columna." But the calicles differ in almost every respect (see p. 43). 

 A fictitious resemblance is given to the two by the dead surface in both being covered with 

 small worm-tubes, as shown in Dana's figure. There are also corals, shells, oysters, and 

 balanids on these specimens. 



This columnar growth-form may be reached along several different lines of development ; 

 in this case we have the sides nearly smooth, and the different growth periods are only 

 betrayed by the ribands of epitheca. 



The spiral twisting of the septa is of interest, but the only clue to its cause is seen in the 

 lateral calicles, where the septa, when they reach the wall, tend to bend round, so as all to run 

 out as parallel stria; to the edge of the living colony. This twist seems to persist in the 

 calicles long after they have left the edge, and even in calicles which never formed any part of 

 the edge, but budded on the summit. The twisting of the septa is a common phenomenon 

 among the Stony Corals. Attention was called to it in TurMnaria, see Vol. II. p. 13. 



a. (Thick compressed column.) Zool. Dept. 88. 11. 25. 19. 



b. (Round column, and showing what appears to 



have been an irregular start upon an 



explanate Montipora.) „ „ 88. 11. 25. 15. 



56. Goniopora Maldives (4) 1. (PI. VII. fig. 1 ; PI. XIII. fig. 6.) 

 [Addu, 32 fathoms, coll. Gardiner ; Cambridge University Museum.] 



Dacription. — Corallum forms groups of thin encrusting colonies, not however always 

 closely adhering, with rounded or straggling outline, and with smooth slightly convex upper 

 surfaces. The group may be formed by an original colony dividing up, each continuing to 

 expand and divide, covering over former dead colonies, until a rounded mass, full of irregular 

 hollows opening in spaces between successive growths, is built up. The edges of the colonies 

 are sharp and frequently with slightly projecting epitheca. 



The calicles vary from 2 to 3 mm., are almost obsolete, and, as is usual in these encrusting 

 forms, appear to be built of radially arranged granules (cf. figures and descriptions of 

 Goniopora N. W. Australia 2, p. 60, G. China Sea 2, p. 71). They show the typical septal 

 formula, and the granules which seem to form the septa increase in size near the wall. 

 Considerable variation occurs in the calicles of the different colonies, variations probably due 

 to differences of position. In some, which appear to have been low down near the under 



