XIII. Odontocyathus Moseley. 



Odontocyatlius Moseley, Challenger Deep Sea Madreporaria p. 14S. 



There are three dead and broken specimens in the collection which are referable to this 

 genus rather than to Stephanotrochiis. 



Synopsis of the Siboga species of Odontocyathus. 



I. Corallum a bowl standing on legs formed by the six primary costje: 



1. Septa strongly exsert, edge of bowl deeply scallopped i. 0. sexradiis. 



2. Septa little exsert, edge of bowl not scalloped 2. Odontocyathus sp. 



II. Corallum perfectly flat, converted into a star by the six large horizontal 



septa and costse of the first cycle I- 0. Stella. 



26. Odontocyathus sexradiis n. sp. Plate III. Fig. 20, 20a — d. 

 Stat. 156. 0° 29.25., I30°5'.3E. 469 m. i Ex. 



The corallum is bowl-shaped, with the edges very deeply scallopped between the enor- 

 mously exsert primary septa, and is supported on six long, strong, solid, smooth, radiating 

 legs, which correspond in situation with the primary septa. 



The costse are but little more than ridges marked only on the sides of the bowl, not 

 on the base where there is a smooth mammillar scar. 



The septa are in six systems and five cycles, with a sixth cycle developed in some of 

 the quarter-systems. Those of the first cycle are the largest and and far the most exsert, and 

 they carry up with them tho.se of the inferior cycles lying immediately on either side of them, 

 which therefore are more exsert than all the other .septa of the same and higher cycles below 

 the first. The septa of the fourth cycle unite with those of the third some way before the 

 latter reach the columella. 



Pali are present, in three crowns, opposite the first three cycles of septa, and in those 

 half-systems in which a sixth cycle of septa is partially developed there are also pali opposite 

 the fourth cj'cle. The pali of the innermo.st crown are the smallest, and those of the outermost 

 crown are the largest. 



There is an abundant fasciculate or radiculate columella, with which the first threis 

 cycles of septa unite. 



Major diameter of calicle 43 millim. 



Minor „ „ „ 34 , 



Greatest height, to summit of the exsert primary septa 28 „ 

 Least height, in interval between two primar)' septa .18 „ 

 Length of rootlets over 20 „ 



This species is evidently very closely related to Stephanotrochiis Tatei Dennant, from 

 the South Australian Tertiaries (Trans. Roy. Soc. S. Australia XXIIL 1898 — 99, p. 117, 

 PI. III. Figs. la—c). 



