154 MADREPORAKIA. 



irregularly jagged or denticulate, tending to be reticular. Tiie septal strise have toothed edges ; 

 in the deeper calicles, the teeth naay lengthen into smooth, bent spines, pointed or forking. 

 These, seen from above, obscure the columellar tangle. But, in the shallower calicles on less 

 convex stocks, the septal teeth are more granular and frosted, and join a large columellar tangle 

 with the usual palic formula, the septa themselves also showing, in such calicles, the typical 

 formula. 



There are tliree specimens showing .striking variations, which, however, appear all to be 

 due to accident. 



The smallest, a, is the least convex, the calicles are about 3 mm. across and about 2 mm. 

 deep, and the septal teeth or plates and the pali are frosted granular knobs, the septal formula 

 being complete. We have, in fact, the primitive * calicle with the walls somewhat raised into 

 thin latticeworks, roughened by the vertical septal stris3. Specimen h shows on one side a 

 dead colony with the characters of a, but on the other a fresh colony which is apparently 

 budding so rapidly that all the calicles are much smaller. The walls are thinner and slightly 

 taller. The colony c is very convex, and the calicles on the top are very deep and as much 

 as 4 mm. across. Instead of the columellar tangle, the base of the fossa is occupied by 

 spinous, slightly-forking septal teeth, which project progressively fui-ther into the fossa. In 

 these deep calicles there is a tendency for the primary septa to be rather more conspicuous 

 than the secondaries. 



Assuming that we are right in putting these together, they show how sensitive the calicles 

 are to slight variations in growth-form, and even speed of growth. They are all tliree com- 

 paratively simple, and fortunately show serial variations on the primitive colony and calicle. 

 The calicle tends to produce higher and thinner walls as the convexity of the colony increases. 

 Compare diagram E, fig. 2, p. 24, Vol. IV. 



a, h, c. Zool. Dept. 1903. 4. 3. 5-6-7. 



162. Goniopora Torres Strait 1. {G. Australim aquilonana prima.) (PI. VIII. fig. 7a.) 

 [West Island, coll. H.M.S. " Alert " ; British Museum.] 



Dcsc7i2^tion. — The corallum is very thin, and encrusting, with tliin, sharp edges hanging 

 free ; from 3 to 5 mm. tliick in the central part. 



The calicles, hardly visible in the coral when freed from organic matter and bleached, are 

 2 mm. in diameter, as slight concave depressions sometimes hardly traceable to the naked eye. 

 Tlie walls are the low, rather liruail, but often hardly discernible ridges between the depres- 

 sions. Their tops appear rather smooth, and to consist of an irregular arrangement of large, 

 squarish or angular flat- tapped granules, as continuations of tlie squarish granules wliich run 

 along the upper edges of the septa. These latter diminish gradually in size towards the centre. 

 The septa themselves run regularly side by side, showing faintly the typical formula, but, at 

 least in the calicles near the edges of the stock, the calicle centre is excentric, and the longer 

 septa show a tendency on each side of the directive plane, to cui-ve round upon the shorter 



• See Vol. IV. p. 19. 



