REPORT ON CORALS — DEEP-SEA MADREPORARIA. 



155 



Stephanotrochus nobilis, Moseley (PI. III. figs. 3, a, J>). 



Ceratotrochus nobilis, Moseley, Proe. Roy. Soc, 1876, p. 554. 



The corallum is white, and is deep and cup-shaped. There is a short curved peduncle 

 at the centre of the base, with a small scar of attachment. An area round the peduncle 

 representing the bottom of the cup is roughened by concentric ridges and toothed costae ; 

 beyond this area the wall of the calicle is smooth, and the costse devoid of teeth. The 

 smooth area is that which in the recent state of the Coral is covered with a living mem- 

 brane reflected from the margin of the calicle ; the roughened area, which is also somewhat 

 discoloured, is in the recent state of the coral bare of living tissue. The teeth on the costae 



Stephanotrochus nobilis (Moseley). Slightly enlarged. 



Diagram showing the arrangement of the septa in Stephanotrochus 

 ■nobilis, and the relative extents to which the various septa are 

 exsert and joined to one another. The septa of the various orders 

 are denoted by nunibersi 



are probably produced in succession as the calciferous membrane is withdrawn from the apex 

 of the base to successively greater distances as growth proceeds. Only the primary and 

 secondary costae are well marked. They are, within the discoloured area, beset with small 

 denticulations, just as in Stephanotrochus diadema and Stephanotrochus discoides. At 

 the verge of the area they almost disappear, but rise again towards the margin of the calicle, 

 as smooth-edged thick laminae, which are directly continuous with the exsert septa. 

 There are six systems and five cycles. The primary and secondary septa are equal, and 

 are prominently exsert, with rounded upper margins. The free margins of the septa are 

 at first nearly vertical, then curve gradually inwards towards the base of the calicle, the 

 fossa is thus remarkably deep and widely open ; there are indications of paliform lobes on 



