REPORT ON THE ASTEROIDEA. 



177 



Chorology of the Genus Craspidaster. 



a. Geographical distribution : — 



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

 40° N. 



Craspidaster hesperus off Japan and China, and in the Eastern 

 Archipelago. 



/?. Bathymetrical range : Appears to be confined to the Littoral zone : 20 fathoms is 

 the greatest depth recorded. 



-y. Nature of the Sea-bottom : Mud. 



Ghorological Synopsis of the Species. 



1. Crasp>idaster hesperus, Mliller and Troschel, sp. (PI. XVII. figs. 5-7 ; PI. XVIII. 

 figs. 1-4). 



Archaster hesperus, Miiller and Troschel, 1840, Monatsber. d. k. Akad. d. Wiss. Berlin, p. 104 ; System 



der Asteriden, 1842, p. 65. 

 Stellaster sulcatus, Mobius, 1859, Neue Seesterne des Hamburger und Kieler Museums, p. 11, Taf. iv. 



figs. 1 and 2 (Abhandl. a. d. Gebiete Naturw. hrsg. v. d. naturwiss. Verein, Hamburg, Bd. iv. 



Abth. 2, I860). 



Rays five. R=53 + mm. (the terminal plate being broken off in all the rays of the 

 largest specimen) ; r= 15 mm. Breadth of the ray across the second supero-marginal 

 plates, 14'5 mm. 



General form depressed and rigid. Rays moderately long and flat, tapering from the 

 base to the extremity, which is not attenuated or sharply pointed. Interbrachial arcs 

 wide and well rounded. Abactinal surface plane. Actinal surface plane. Margin well 

 rounded ; lateral walls highest in the interbrachial arc, decreasing gradually towards the 

 end of the ray. 



The abactinal surface of the disk and rays is covered with paxilla3 of a rather peculiar 

 form, which I have not observed in any other species. In the immediate centre of the 

 disk the paxillse are small, crowded, and individually indistinguishable ; they also 

 diminish greatly in size as they proceed along the ray, but remain perfectly distinct, and 

 though closely placed throughout, in no way interfere with one another's form by crowd- 



(ZOOL. CHALL. EXP. — PART LI. — 1887.) 23 



