MADREPORARIAN CORALS 333 



Six septa (I) thicker and fused in the centre of the caUce. The next six (II) much 

 thinner, extending about two-thirds of the way to the centre. Twelve (III) still thinner 

 and joining septa I at about two-fifths of their breadth. Lastly, cycle IV generally 

 represented only by costae, alternating with those of I, II and III. 



Upper edges of all septa rising above the theca evenly. Septa of I with markedly 

 upstanding edges, extending from the fusion with septa III almost to the depressed 

 columella in the centre of the calice. 



Genus Sphenotrochus Ed. and H. 

 Sphenotrochus intermedius (Munster). 



Ed. and H., Ann. Set. nat. ser. 3, ix, 243 (1848); Cor. II, 68 (1857). Duncan, Trans. Zool. Soc. 

 vni, 320, XLI i-s (1873).! 



St. 388, 121 m., 7, one alive and the rest recently dead; St. 934, 100 m., one living, 

 1 1 mm. high with calice 7 by 3 mm. 



A series of much larger coralla than those of the 'John Murray' Expeditmi (p. 192), 

 the Hving form from St. 388 being 7 mm. high, calicle 6 by 2-5 mm., the dead forms from 

 same larger. There are three cycles of septa complete and in the larger forms the directive 

 septa at the ends of the elongated calice may have pairs of septa IV on either side, in one 

 corallum even some of septa V while at the sides of the calice there are only septa I-III. 



The costae are well marked ; new costae may look as if they arose by branching of the 

 lower costae, viz. those near the base of the corallum, but the terminal costae belonging 

 to the directive septa at the ends of the flattened calices never branch and are very 

 conspicuous. The columella is a central plate along the calice and is joined by the ends 

 of septa I and 11; it is capped by a series of upstanding, rather rough pillars, shown best 

 in the two living forms. 



Genus Deltocyathus Ed. and H. 

 Deltocyathus lens Alcock. 



' Siboga' Exp. p. 19, II 16 (1902). 

 A single specimen from St. 939, 87 m. It is a corallum that has regenerated from a 

 broken fragment with 7 costae. The chevron-formation of the septa is little marked. 



Genus Madracis Ed. and H. 



The genus may be branching, or incrusting, or a mixture of both. The surface is 

 covered with calices which are closely packed and small. The septal number is ten of 

 equal size, all fusing internally with a styliform-columella. The calices are closed in 

 below by tabulae regularly arranged as transverse partitions, and there is no other 

 filling up of their cavities. 



The above characters apply to the following species: ospenila Ed. and H., hellana 



Ed. and H., decactis (Lyman) Verrill, pharensis Doderlein and singidaris Rehberg, if my 



1 Duncan's figures illustrate the shape and texture well. I expect Marenzeller's aurantiacus (' Valdivia ' 

 Exp. p. 280, XVIII 15) is a synonym, but I have not a long enough series to be assured. The same remark 

 applies to S. auritus Pourtales {' Hasslar' Exp. p. 37, 1874). 



