376 THE VOYAGE OF H.M.S. CHALLENGER. 
B. Marginal plates equal to or smaller than the other plates. 
a, Papule distributed throughout the abactinal area. Abactinal plates 
thick, crescentiform, devoid of internal processes . 2 . ASTERININE. 
a. Abactinal plates not imbricated ; covered with spines. 3 { Patiria. 
b. Abactinal plates imbricated throughout the abactinal area, or 
only in definite regions. 
a. Rays cylindrical, more or less elongate. Disk small. 
With a definitely and sharply defined band of 
crescentiform plates along the median area of 
the rays. 7 4 : : c : ; ° Nepanthia. | 
8. Rays and body flat. Disk large. 
i, Abactinal plates more or less imbricated through- 
out, and bearing spinelets at the free edge, or 
covered with granules. All the abactinal 
plates subsimilar . : : < : Asterina. 
ii. Abactinal plates imbricating only near the 
margin, the others spaced apart ; covered with 
naked skin . : Fi . . : ; Disasterina. 
b. Papule confined to the radial regions, Abactinal plates in the median 
regions stellate. Abactinal plates thin, scale-like, with elongate 
internal prolongations . : : : r . PALMIPEDINE. 
a. Abactinal plates bearing tufts of epincloie No membrane or 
granules. Papule in a single row on each side of the 
median radial line . : : é 3 Palmipes. 
b. Abactinal plates covered with ci ratnate porns granules. 
No tufts of spines. Papule in several rows on each side 
of the median interradial line ‘ : : : ‘ . Stegnaster. 
Subfamily Ganertin.4, Sladen, 1888. 
Genus Cycethra, Bell. 
‘Cycethra, Bell, Proc. Zool. Soc. Lond, 1881, p. 96. 
This genus was established by Professor Jeffrey Bell for the reception of a starfish dis- 
covered by Dr Coppinger in Trinidad Channel during the surveying voyage of H.MLS. 
“Alert” in the Strait of Magellan and on the coast of Patagonia. The remarkable com- 
bination of characters presented by that form was noticed by Bell, and duly referred to 
in his description ; and the new species appear to fully bear out the “mixed” character of 
Cycethra as regards its morphological relationships. ‘The genus would seem to have a 
limited distribution, but appears to possess a considerable amount of specific plasticity 
within that area. Its alliance to the very local genus Ganeria is striking, and when the 
two forms are studied together, I think there will remain little doubt that Cycethra 
and Ganeria are near neighbours in the zoological scale as well as in geographical 
position. 
