256 MB. W. PE ECT SLADEN" ON THE 



breadth of the plates is very little greater than the length on the 

 inner portion of the ray ; and on the outer portion these propor- 

 tions are reversed. 



Infero-marginal plates broad, gently rounded on to the actinal 

 surface, and do not extend beyond the superior series. Marginal 

 spines 3, placed close together in a very oblique series, the 

 second from the margin being slightly longest and most robust; 

 all are exceedingly delicate, needle-like, and very faintly bent, 

 the longest being rather more than twice the length of the 

 plate. On the three innermost plates the upper or outer spine 

 is the longest ; it is also flattened and much broader than else- 

 where. Excepting on the three innermost plates no other spines 

 occur ; on these, however, one or two very small ones are present in 

 the median line. The surface of the infero-marginal plates is 

 covered with numerous minute papilliform squamules closely 

 placed, which become more spiniform towards the margins. 

 Yentral plates not more than two or three present, covered with 

 short papilliform spinelets similar to those just noticed. 



Ambulacral spines short, delicate, cylindrical, slightly tapering 

 at the tips, forming two series. The inner series consists of 

 three spines; the middle slightly longest, radiating apart and 

 directed over the furrow. The outer series consists likewise of 

 three similar and equal spinelets usually directed towards the 

 margin of the ray ; and occasionally there may be one or two 

 supplementary spinelets, usually smaller, and almost indistin- 

 guishable from the spinelets of the infero-marginal plates ; occa- 

 sionally one is as large as the three spinelets of the outer series, 

 and is irregular in position. 



Mouth-plates small, and form a prominent narrow keel along 

 the median suture-line, on either side of which are borne two 

 rows of rather elongate cylindrical spinelets, 6 or 7 in each, 

 and 2 or 3 in single series on the outer part, which are larger. 

 The innermost spinelets are more robust than the others, but 

 only very slightly longer, and no prominent horizontal comb is 

 formed over the mouth-opening as in other species. There is a 

 row of 5-7 rather elongate spinelets on the free margin of the 

 mouth-plate. 



The paxillar area has a comparatively open and irregular ap- 

 pearance in consequence of the character of the paxillte ; these 

 have short thin pedicels scarcely forming a true tabulum, and 

 are surmounted by 8-10 rather long delicate spinelets, much 



