Prof. F. J. Bell oh British OpMurids. 339 



a few sj)inc.s which may be present on the inner side of tlicir 

 base. Each is separated from its fellow by a few laterally 

 compressed scales on which are spinous j^ranulcs or short 

 spines. The tcerli-j)apilke arc exceedingly numerous, and 

 beneath the clump are seven teeth. The arms are rather 

 delicate ; the upper ann-])lates have a concave proximal and 

 a strongly convex distal edge ; the upper surface is carinate 

 and the distal end of the keel forms a knob. The side arm- 

 plates extend considerably on the proximal part of these 

 plates and carry about seven spines, of which the uppermost 

 is shorter than the next three or four, but not so short as the 

 lowermost two or three. There is one tentacle-scale. The 

 underarm-plates have the distal edge wider than the proximal 

 and often concave outwards. 



Oijhiothrix Luetkenij Wyv. Th. 



A stout, well-grown species. Arms about ten times as 

 long as the radius of the disk. The scales on the disk not 

 unlike those of O.fragilis^ and, as in it, they may or may not 

 be covered with spines. The interbrachial spaces have the 

 middle third occupied by fine spines, the sides bare. The 

 triangular radial sliiclds differ chiefly from those of 0. frajilis 

 in not having the spines or spinous granules contined to one 

 angle. Teeth-papillae coarse. Arms bvoad, flat, strong. 

 The upper arm-plates somewhat variable in form, but always 

 with a few fine spines, hardly at all carinate, with pretty even 

 proximal and distal edges. S[)ines coarser and rather shorter 

 than in O.fragilis, about seven in number. The lower arm- 

 plates with a concavity outwards, but this is not very obvious 

 in full-grown specimens. One tentacle-scale. 



Colour white or banded and spotted with red or purplish. 



The difference in size, the stouter arms and coarser spines, 

 the bare interbrachial spaces, the spines on the radial shields 

 and upper arm- plates, the loss of the keel, are sufficient to 

 justify the distinctness of 0. Luetkeni, at any rate in the 

 present state of our knowledge. 



2. The Use of the Generic Term Ophiura. 



Since the commencement of his important work on Ophiurids, 

 Mr. Theodore Lyman lias used the name Oj^hiura for those 



23* 



