REPORT ON THE ASTEROIDEA. 295 



Remarks. — The group of species which I have classed in this genus form two very 

 distinct sections, one of which may perhaps ultimately be considered worthy of being re- 

 cognised as a subgenus, if it be not actually accorded generic rank. From the scantiness 

 of the material now available, I have not, however, felt justified in taking this step at 

 present, but merely indicate what seems to me may be the possible future requirement of 

 the case when a more extensive series of specimens can be studied. 



Synopsis of the Species included in the Genus Nymphaster herein described. 



A. Supero-marginal plates separated throughout the ray by a median abactinal series of 



plates. Plates of the abactinal radial areas distinctly paxilliform. Entrenched 

 pedicellariaB present. 



a. Radial paxillae with a large number of central granules. Rays comparatively 



Ion" ............. symbolicus. 



b. Radial paxillae with only two central granules. Rays comparatively short . bipunctm. 



B. Supero-marginal plates united in the median abactinal line throughout the ray. Plates 



of the abactinal radial areas very slightly tabulate. No entrenched pedi- 

 cellariaB present. 



a. Adambulacral armature with a secondary series of spinelets on the actinal sur- 



face of the plate protentus. 



b. Adambulacral armature with no secondary series of spinelets ; granules only on 



the actinal surface of the plate. 



a. Radial paxillae hexagonal ; with pedicellariae basilicus. 



b. Radial paxillae circular ; bearing no pedicellariae .... albidus. 



So far as I can judge from the information published, I am inclined to think that 

 the following forms will ultimately be associated with the species I have placed in this 

 genus, viz. Dorigona subspinosa, Perrier, Dorigona arenata, Perrier, Dorigona temalis, 

 Perrier, Dorigona prehensilis, Perrier, and Pentagonaster (Dorigona) moebii, Studer. 

 Probably Pentagonaster alexandri, Perrier, may also be included in the same category ; 

 and perhaps the form described under the name of Astrogonium fallax, Perrier, as well. 

 Pentagonaster elongatus, Perrier, is another doubtful form, but from the description 

 given appears to me to be more nearly related to one of the species I have placed in 

 the genus Paragonaster, in which I venture to think it will ultimately be classed. 



Chorology of the Genus Nymphaster. 

 Geographical distribution : — 



Atlantic : Three (or probably nine) species between the parallels of 40° N. and 

 20° S. 



Nymphaster albidus, off the Cape Verde Islands. Nymphaster 

 protentus, south-west of the Canary Islands. Nymphaster basilicus, 

 off the west coast of Brazil. 



