HOLOTHTJRIOIDEA OF THE INDIAN OCEAN. 85 



Internal Structure. — The calcareous ring is of the usual type. 

 I am unable to detect the Polian vesicle and stone canal, but 

 Semper describes the presence of the Polian vesicle and one 

 stone canal. Cuvierian organs are present. 



Spicules. — These consist of tables in the general integument, 

 and according to Semper smooth buttons with three pairs of 

 holes around the base of the ambvilacral appendages. There 

 are also elongated perforated plates supj)orting the appendages. 

 The tables measure 44 ^. across the disc. The disc has 

 typically a large cross-shaped hole in the centre, four parts 

 of which reach the periphery, and alternating with these are 

 four smaller holes. The disc is subject to variation in regard 

 to this. When the tower is complete, which is rare, it is 

 surmounted by a square top which bears several spines, the 

 four largest being placed one at each corner. The tower is 

 low, being only about 25 t*- in height, and seems to have a 

 variable number of supports. The perforated supporting rods 

 of pedicels are 80 \^ or more in length. They are veiy broad 

 in the middle and bulge slightly at each end. 



Distribution. — Samoa and Maldives. Only three specimens 

 of this species are known. The first two were described from 

 Samoa in 1868, and the other specimen was not obtained until 

 thirty years later from the Maldives. Considering the great 

 distance between these two localities it is surprising that no 

 specimens have been recorded from intermediate stations 

 during a period of thirty years. 



HoLOTHURlA IMPATIENS (Forskaal). 

 (Plate XIIL, fig. 21.) 



Fistularia impatiens, Forskaal 1775. 



Trepang impatiens, Jager 1833 (14). 



Holothuria fulva, Quoy & Gaimard 1833 (36). 



Thyone impatiens, BlainviUe 1834. 



Sporadipus impatiens, Grube 1840. 



Holothuria bolellus, Selenka 1867 (37) ; Semper 1868 (38). 



