384 BULLETIN 76, UNITED STATES NATIONAL MUSEUM. 



Pteraster, beiii<i free on one margin only. The mouth plates are also different. 

 Both species are from the Southern Ocean, west of theCrozet Islands, 1,375 fathoms. 

 In this section of Hymen aster must be ranged //. platyacanthus Ludwig and H. 

 furpureus Ludwig from the Panama-Galapagos region. Without a direct com- 

 parison of specimens it is not possible to determine the validity of these forms, as no 

 specific characters are figured. //. phtyacantlms differs apparently in having a 

 thin and tender supradorsal membrane, seven instead of nine rows of alternating 

 paxillif, deposits in the abactinal integument at base of papulae, and in having the 

 papuhv in the middle insteatl of in the corner of the meshes (some of the lateral 

 papulae are in the middle of the mesh in quadrispinosvs) . The deposits may be 

 present only in old specimens, and I am not sure that the position of the papulae 

 may not vary. H. purpureus differs from platyacantlius according to Ludwig 

 (1905, p. 196) in having a dark color, and a membraneous lappet or sacculus at the 

 tip of the aperture papilla?. These differences are very trifling, as color is in star- 

 fishes an almost useless character, and the sacculus varies with age in quadnspinosus. 

 H. purpiiretts is, perhaps, the same species as //. quadnspinosus, but I hesitate to 

 place it in synonymy without specimens or figures for comparison. 



