REPORT ON CORALS—DEEP-SEA MADREPORARIA., 155 
Stephanotrochus nobilis, Moseley (Pl. II. figs. 3, a, 6). 
Ceratotrochus nobilis, Moseley, Proc. 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 costee ; 
beyond this area the wall of the calicle is smooth, and the coste 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 costee 
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 numbers. 
are probably produced in succession as the calciferous membrane is withdrawn from the apex 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 cost 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 ealicle, 
as smooth-edged thick laminz, 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 
