REPOKT ON THE ASTEEOIDEA. 353 



■and I have therefore referred the material now in my hands for description to the first 

 described species. 



Genus Asterodiscus, Gray. 

 Asterodiscus, Gray, Proc. Zool. Soc. Lond., 1847, Part xv. p. 75. 

 This genus, although a near ally of Culcita, is well marked, and may readily be dis- 

 tinguished from all other forms. The character of its abactinal tegumentary structure, 

 and the presence of the pair of large marginal plates at the extremity of the rays, separate 

 it generically from the other members of the family. Only one species is at present 

 known. 



Chorology of the Genus Asterodiscus. 

 a. Geographical distribution : — 



Eastern Archipelago and Pacific : One species between the parallels of 0° and 

 30° N. 



Asterodiscus elegans, from Samboangan and N. E. China. 

 /3. Bathymetrical range : Shallow water. 

 y. Nature of the Sea-bottom : Not recorded. 



Chorological Synopsis of the Species. 



1. Asterodiscus elegans, Gray. 



Asterodiscus elegans, Gray, 1847, Proc. Zool. Soc. Lond., Part xv. p. 75; Ann. and Mag. Nat. Hist., 

 1847, p. 196; Synop. Spec. Starf. Brit. Mns., 1866, p. 5, pi. xii. figs. 1 and 2. 



Locality. — Station 212. Off Samboangan, Philippine group. Depth 10 fathoms. 



Remarks. — The example collected by the Challenger has more numerous prominent 

 tubercles on the abactinal area than Gray's figure represents ; and the median radial line 

 is not so definite. The adambulacral armature consists of (1.) a furrow series of five spines 

 (the adoral one small and often hidden) ; and (2.) on the actinal surface of the plate a 

 transverse series of three robust, papilliform spines on the inner half of the ray and of 

 two on the outer half (the outermost often with one small, irregular, prismatic granule on 

 each side). A pedicellaria with two elongate jaws often stands on the adoral side of the 

 first or second of the spines on the actinal surface of the plate, or opposite their inter- 

 space, on the middle or outer third of the furrow. Numerous pedicellaria?, with delicate 



(zool. chall. exp. — PART LI. — 1888.) 45 



