REPORT ON CORALS— DEEP-SEA MADREPORARIA. 151 



are very conspicuous and prominent, those of the third cycle being as usual the largest 

 and projecting to a height of 4 mm. above the level of the summit of the columella, 

 whilst those of the primary cycle are not elevated more than 1'5 mm. above that point. 

 The tertiary pali are broad, the secondary and primary much narrower. The superior 

 margins of all the pali are rounded. In some specimens all the pali are slightly indented 

 on their inner edges. The pali of the secondary septa are placed at a slightly further 

 distance outwards from the centre of the columella than those of the primary. The pali 

 thus form three rings or crowns. Wherever a pair of septa of the partial fifth cycle arc 

 developed, the quaternary septa intervening between them are greatly enlarged, and 

 occasionally fused with the adjoining tertiary septa. They are also provided with pali 

 somewhat smaller than those of the tertiary cycle, and placed at a slightly further 

 distance from the axis of the coral. The whole of the septa and pali are formed of thin 

 but strong laminae slightly thickened at the line of origin from the calicle, and terminating 

 superiorly in sharp knife-edged margins. The surfaces of the septa and pali are covered 

 with very small granular projections, which on the primary and secondary septa are seen 

 to be arranged with considerable regularity in rows, radiating from a point a little 

 inferior to the point of junction of the septa with the margin of the calicle towards the 

 margin of the septa, and marking out also a series of successive lines which follow the 

 course of the margins of the septa, and are the lines of growth of the septa. Similar lines 

 of growth are to be observed on the pali. The columella is about 4 mm. in breadth, and 

 is composed of a number of contorted papillae covered with a fine granulation, and more 

 or less fused into a single tubercular mass in old specimens. 



Diameter of calicle of smallest specimen 15 mm. Height, exclusive of conical 

 tubercle on base, 8 mm. Diameter of calicle in largest specimen 27 mm. Extreme 

 diameter of the same measured from the outer edges of the summits of the exsert septa 

 32 mm. Height of calicle 16 mm. ; measured to the top of the septa 20 mm. Diameter 

 of base of calicle 21 mm., of circlet of basal spines 28 mm. 



Stephanotrochus, n. gen. 



Corallum dense and compact in substance, cup-shaped or saucer-shaped, with trace of 

 early attachment, usually with well developed costse bearing a succession of small spines, 

 with widely open capacious fossa. Septa usually extremely exsert, the exsert quinaries, 

 or quaternaries where these are not present, lying next to the primaries, higher than 

 the tertiaries, or equal to them. Columella absent or little prominent. 



I have formed this genus to contain four species of corals dredged by the Challenger 

 which are evidently very closely allied, but for which it is nevertheless somewhat difficult 

 to find generic characteristics in the terms of the ordinary designation of genera. I placed 

 the four species provisionally in my Eeport on Corals in the genus Ceratotrochus. 



