?4 

 2 7- Odontocyaihus ? sp. 



Stat. 262. 5°53'.8S., i32°4S'.8E. 560 m. 1 Ex. 



This is a small dead and damaged specimen, which may possibly be the young form 



of the previous species. It has six small roots, one of which has got out of place. The septa 

 are little exsert, so that the edge of the bowl is not scallopped. 



28. Odontocyaihus stella n. sp. Plate III., fig. 21, 2 ia — 1>. 



Stat. 159. 0° 59/1 S. I29°48.'8E. 411 m. 1 Ex. dead and broken. 



This species, like Odontocyaihus sexradüs, has a very close resemblance to Stephano- 

 trochus latei Dennant. It is, however, even flatter than 5. tatei and has fewer septa, while the 

 combined septa and costae of the first cycle besides being more prominent and exsert are horizontal. 



Corallum flat, star-shaped owing to the remarkable extension outwards of the large and 

 strong costse and septa of the first cycle. 



The basal wall is covered with fine discrete granules. There is a central scar of attach- 

 ment, from which six strong costae radiate horizontally like the spokes of a wheel. Costae 

 corresponding to the lovver cycles of septa exist only near the edge of the hexagonal disk. 



The septa are in six regular systems and four cycles, with traces of a fifth. Those of 

 the first cycle are the highest and largest, and with the corresponding costae form the great 

 compressed spokes or rays which, projecting far beyond the edge of the disk, form the cha- 

 racteristic feature of this species. Those of the 2 nd and 3 vd cycles are about equal to one another 

 and unite near the columella. Those of the 4" 1 cycle are free, and do not reach the columella. 



The edges of all the septa are ragged and their surface is echinulate ; and as the 

 margin oi the hexagonal disk is somewhat concave between the great ray-like primary septa, 

 the septa of the 2 nd cycle are the least exsert of all but the quaternaries that lie immediately 

 on either side of them. 



Ragged paliform teeth are present in front of all the septa except those of the last (fourth) cycle. 



The columella consists of a tortuous network of criply granular processes. 



Maximum diameter of disk 12 millim. ; span of corallum between the tips of opposite 

 spokes 21 millim. 



XIV. Stephanotrochus Moseley. 

 Stephanotr ochus Moseley, Challenger Deep Sea Madreporaria, p. 151. 



This genus is represented in the collection by 4 specimens, two of which are deacl and 

 broken coralla which can not be exactly determined, though the)- possibly belong to 5. weberianus. 



Synopsis of the Siboga species of Stephanotrochus. 



I. There are 12 large and strongly exsert septa, and the septa of the inferior 



cycle immediately on either side of them are themselves remarkably exsert. 1. 5. weberianus. 

 II. There are 21 large and much exsert septa, and the septa of the inferior cycle 



immediately on either side of them are not more exsert than the others. 2. 5. Sibogce. 



