ECHINODEBMATA. 511 



3 A' -, -which seems to be new to science, bnt ofwticli more mature 

 (I ^ 



specimens must be obtained before the species can be named and 



described. 



From the He des Eoches, which is on a separate coral-bank from 

 the other islands, came : — 



Phyllacanthus baculosus (13 fms.). 



At Providence Island, which is 240 miles S.W. by S. of the 

 Amirante group, the only Echinoderm obtained was 



Ophiothrix propinqua. 



This species seems to be somewhat variable in the details of its 

 coloration ; originally described by Lyman as having a blue mark- 

 ing, some specimens collected by the ' Challenger ' were reported by 

 that eminent authority as " red varieties." Such are most of the 

 specimens in the present collection. 



From Glorioso Islands come : — 



Ophiocoma scolopendrina and Holothuria pardalis. 



In addition to thfi more or less well-known species of Ophiurids 

 the names of which have just been given, the collection contains 

 examples of some very remarkable forms which, so far as I am able 

 to teU, have not yet received description at the hands of any 

 naturalist. 



In one case I feel justified in establishing a new genus, for 

 which, as the term E&m,iplax is already in use, I propose that of 

 Neoplax. 



NEOPLAX. 



Disk covered with a rather thick skin, not richly granulated. No 

 radial shields; the dorsal arm-plates present, but incompletely 

 developed and not touching one another. Arms long, slender, 

 coiled on themselves, but not divided. A few mouth-papillse' and a 

 few teeth, but no fringe of spines to either. A moderate number of 

 short arm-spines, with their basal portions embedded in the skin. 

 The tentacle-scale single and very small. The genital slits long 

 and the scale large. 



This interesting genus appears to belong to Mr. Lyman's third 

 group of OphiuridsB, or the Astrojphyton-Yike Ophiurans. Notwith- 

 standing the absence of radial shields, it does not seem to have any 

 special afiinity to Ophiormjces ; but, on the whole, to stand not very 

 far from Ophiowyxa, from which, however, it is to be distinguished 

 (1) by the complete absence of radial shields, (2) the great reduction 

 of the plates at the margin of the disk, (3) the twisted arms, and 

 (4) the absence of the modified spines on the oral processes. 



