204 ME. W. PEECY SLADEN OK THE 



Ambnlacral furrows rather broad, not petaloid, tapering towards 

 the extremity. Sucker-feet arranged in simple pairs. Ambu- 

 lacral spinelets 5, long, acicular, webbed together into trans- 

 verse or obliquely curved combs, and remarkable for their posi- 

 tion more than half within the furrow. Spines of unequal length, 

 the innermost much smaller than any of the others, and placed 

 somewhat in advance of, or aboral to, the series ; the longest 

 spine usually the middle one, or sometimes the second from the 

 outside, in length nearly equal to the breadth of the furrow, 

 across which it stretches horizontally, whilst the two outer spines 

 radiate downward and aborally. Consequent on this position of 

 the median spine, the spinelets which compose the outer half of 

 the comb radiate very widely apart. The connecting web is fine 

 and semitransparent, very deeply indented between the spinelets, 

 the combs receiving thereby a remarkable appearance ; and the 

 Aveb is continued from the outer spine of the comb down to the 

 base of the aperture -papiUa, and not out along the actino-lateral 

 spine. The aperture-papilla is represented by a small conical 

 spinelet placed on the outer edge of the adambulacral jDlate and 

 between the bases of the actino-lateral spines ; it is covered with 

 membrane, that of the ventral area being stretched over it, giving 

 it the form of a small subtriaugular or conical peak. 



Mouth-plates of moderate length, with widely expanded lateral 

 flanges. Keel along the line of junction prominent, forming a 

 well-developed peak aborally, hidden beneath the tissue of the 

 ventral membrane, produced into a point adorally. On either 

 side of this, and placed on the horizontal margin of the plates, 

 are three mouth-spines, webbed together, about equal in size 

 with the ambulacral spines, but rather more robust, the inner- 

 most spine on each plate longest, and the other two decreasing in 

 series. Immediately behind the three mouth-spines stands a 

 small secondary superfical mouth-spine, about the same size as, 

 or smaller than, the innermost mouth-spine, with which it is con- 

 nected by a continuation of the web ; the pseudo-comb being 

 thus bent upon itself at a sharp angle, gives a very striking cha- 

 racter to the armature of the mouth-plates. The ambulacral 

 spines that form the comb belonging to the first adambulacral 

 plate have their bases arranged in a semicircular curve, and the 

 spines radiate at equal distances apart and are directed down- 

 wards and adorally, the middle spine being longest. The spines 

 are all webbed together : and a continuation of the tissue from 



