258 ME. W. PERCY SLADEK ON THE 



the third is much less and more compressed. This triplet of 

 spines is confined to the marginal edge of the plate, and no other 

 spines are present, except on one or two of the innermost plates, 

 the rest of the plate being covered with small uniform squamules ; 

 and these, though short, are more or less spatuliform and with 

 rounded tips. Ventral plates only two or three present, bearing 

 small uniform papilliform spiuelets. 



Ambulacral spines short, normally forming two series ; but 

 on some plates the outer series is somewhat irregular, and may 

 simulate the appearance of three series. The inner or furrow- 

 series consists of three spines, of which the middle one is loiogest, 

 straight, cylindrical, and tapering ; whilst the two lateral ones 

 are short, delicate, compressed in the direction of the axis of 

 the ray, slightly expanding towards the tip, and truncately 

 rounded. The outer series are three in number, equal in size, 

 broad, robust, ilatly compressed in the direction of the axis of 

 the ray, widely flaring towards the extremity and truncate. The 

 middle spinelet is on some plates placed external to the two lateral 

 ones, and sometimes, in consequence, appears like a solitary 

 spinelet of a third series. Sometimes also the aboral lateral 

 spinelet may be slightly in advance. On a few of the innermost 

 plates one or two supplementary spinelets may be present. 



Mouth-plates large and prominent, with a single line of short 

 robust papilliform spinelets upon the surface of the keel along 

 either side of the median suture ; these are about 10 or 11 

 in number, and decrease in size ad- and aborally. Of the mouth- 

 spines proper situated on the free margin of the plates, the three 

 innermost on either side of the suture-line are long, robust, 

 cylindrical, obtusely rounded, and form, together with the corre- 

 sponding spines of the companion plate, the comb which stretches 

 horizontally over the mouth-aperture. On the remaining por- 

 tion of the free margin are 3 or 4 small, equal-sized, cylindrical 

 spines. The first adambulacral plate next to the mouth-plate is 

 narrow, with a biserial armature, consisting of about 8 small, 

 compressed, slightly flaring, and truncate spines in each row. 



The paxiUar area is compact and uniform, rather more than 

 three times the breadth of the supero-marginal plates at the 

 middle of the ray. The paxillse are longer on the disk and along 

 the median dorsal line than at the sides of the rays, where they 

 are arranged in regular transverse rows, about 5 in each. The 

 larger paxillse have a circlet of 10-12 short spinelets surround- 



