150 



THE VOYAGE OF H.M.S. CHALLENGES. 



may perhaps prove to belong to this genus, or be nearly allied. The information, how- 

 ever, is too meagre to hazard even a conjectural opinion. 



M. Perrier l records the presence of two species of Styracaster amongst the Asteroids 

 collected by the " Talisman " Expedition. He states that " une de nos especes (Styra- 

 caster spinosus, E. P.) presente un pedoncule dorsal ; l'autre (Styracaster Edwardsi, 

 E. P.) n'a qu'un simple tubercule, mais chacun de ces bras porte sept epines sur la 

 ligne me'diane dorsale." No further remark is made and no description is given of the 

 species ; I am therefore unable to consider them. The second species mentioned would 

 seem to resemble Styracaster horridus. 



Chorology of the Genus Styracaster. 

 a. Geographical distribution: — 



Atlantic : One species between the parallels of 0° and 10° S. 



Styracaster horridus, between the south coast of Africa and the 

 Island of Ascension. 



Pacific : One species between the parallels of 0° and 10° N. 



Styracaster armatus, in the neighbourhood of the Caroline 

 Islands. 



/3. Bathymetrical range: 1850 fathoms to 2350 fathoms. 

 Both species are confined to the Abyssal zone. 



y. Nature of the Sea-bottom : Both Styracaster horridus and Styracaster armatus 

 are found on Globigerina ooze. 



Chorological Synopsis of the Species. 



1. Styracaster horridus, Sladen (PL XXIII. figs. 5-7; PI. XXVII. figs. 17-20). 

 Styracaster horridus, Sladen, 1883, Journ. Linn. Soc. Lond. (Zool.), voL xvii. p. 229. 



Pays five. R = 75mm. ; r=15mm. R=5r. 



Pays very long and slender, compressed laterally, and tapering to the extremity. 

 The disk is not high, although capable of being inflated to a sbght extent above the level 

 of the marginal plates. The minor radius is in the proportion of 20 per cent. The 



1 Comptes rendus, 1885, t. ci. p. 88G. 



