150 THE VOYAGE OF H.M.S. CHALLENGER. 
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’ records the presence of two species of Styracaster amongst the Asteroids 
collected by the “Talisman” Expedition. He states that ‘une de nos espéces (Styra- 
caster spinosus, EK. P.) présente un pédoncule dorsal; lautre (Styracaster Edwardsi, 
E. P.) n’a qu'un simple tubercule, mais chacun de ces bras porte sept épines sur la 
ligne médiane 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 :— 
Atiantic: One species between the parallels of 0° and 10° S. 
Styracaster horridus, between the south coast of Africa and the 
Island of Ascension. 
Paciric: One species between the parallels of 0° and 10° N. 
Styracaster armatus, in the neighbourhood of the Caroline 
Islands. 
8. 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. 
Ocean. | Range in Fathoms. Nature of the Sea-bottom. 
Styracaster armatus. . . | Pacific. | 1850 Globigerina ooze. 
Styracaster horridus. : . | Atlantic. | 2350 Globigerina ooze. 
1. Styracaster horridus, Sladen (Pl. XXIII. figs. 5-7; Pl. XXVII. figs. 17-20). 
Styracaster horridus, Sladen, 1883, Journ. Linn. Soc. Lond. (Zool.), vol. xvii. p. 229. 
Rays five R=75mm.; r=15mm. R=5r. 
Rays very long and slender, compressed laterally, and tapering to the extremity. 
The disk is not high, although capable of being inflated to a slight 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. 886. 
