494 



THE VOYAGE OF H.M.S. CHALLENGER. 



Chorological Synopsis of the Species. 



Synopsis of the Species included in the Genus Hymenaster. 



A. Adambulacral armature consisting of one spinelet. 



a. Paxillae- crowns forming raised areas of membrane. Spiracula small, 



numerous, equidistantly spaced ........ 



b. Paxillae-crowns not forming raised areas. 



a. Spiracula single, large, uniformly spaced 



b. Spiracula in groups of six to ten, small, irregularly distributed 



B. Adambulacral armature consisting of two spinelets. 



a. Muscular fibrous bauds of supradorsal membrane coherently reticulated. 



o. Paxillse-crowns forming definite areas. Spinelets not prominent . 



b. Paxillae-crowns not forming definite areas. Spinelets very prominent. 



a. Spinelets forming a raised keel over each radius. Spiracula 



large, single, distributed ...... 



fi. Spinelets not forming a raised keel. Spiracula microscopic, 

 in groups of ten or more ...... 



b. Muscular fibrous bands of supradorsal membrane simply intercrossing. 



a. Radial areas elevated in relief above the interradial tissue. Paxilla? 



with three spinelets ......... 



b. Radial areas not elevated above the interradial tissue. Paxilla 



with more than three spinelets. 



nobilis. 



formosus. 

 pergamentaceus. 



saceulatus. 



echinulatus. 



glaucus. 



