266 DISCOVERY REPORTS 



actinal, and oral bivalved pedicellariae ; 3 adambulacral spines in a single transverse 

 series ; tube-feet very large ; a dark brown superomarginal band ; R 1 15 mm., r 1 1-5 mm., 

 R= lor; br 8 mm. 



Description. Abactinal area of ray narrow, with 3 regular longiseries of circular 

 spaced paxillae on either side, those of the outermost series representing the supero- 

 marginals. These, except at base of ray, are very much larger than the adjacent abactinal 

 paxillae, of which 8-12 can be counted across ray to the other superomarginal series. In 

 the median abactinal area (4 paxillae wide at base of ray and 8 at middle) regular 

 longiserial arrangement is lost. The paxillae are stellate, not squarish, well spaced, and 

 decrease in breadth and height very rapidly along ray. At base of ray, the lateral, with 

 8-12 slender marginal and 1-3 similar central spinelets are obviously larger than the 

 median paxillae ; but the disparity becomes rapidly less and less, the lateral -most paxillae 

 become very small and the longiserial arrangement less obvious. The largest paxillae 

 with 10-12 spinelets (and very low tabulum) are now in the central area, intermingled 

 with smaller ones (5-8 spinelets). Many paxillae of disk and proximal third of ray carry a 

 central or marginal conspicuous bivalved pedicellaria (Fig. ^b). 



The first 3 superomarginal paxillae are subequal to the lateral abactinal but they 

 rapidly increase in size and the outer margin fuses with the dorsal margin of the infero- 

 marginal. The free border carries 10-12 spinelets and the surface 3-6, of which one, 

 slightly enlarged, constitutes an incipient superomarginal spine. Some of the plates 

 carry a bivalved pedicellaria larger than the abactinal. Corresponding to first 10 

 superomarginal paxillae are 14 lateral; to the second 10, also 14 lateral. 



The inferomarginal plates are heavy, block-like (with deep, wide fascioles), and form 

 a rounded lateral face to ray ; that is, they occupy little of the actinal face of ray. At base 

 of ray, the first 6 or 8 are short and wide ; width rapidly diminishes so that it is only 

 twice length, and continues until at middle of ray and distally the two dimensions are 

 equal, or the width is slightly the greater. Inferomarginal spines acicular, sharp, 

 bristling. Beginning with second to eighth plate, each alternate plate carries 3 spines. 

 The longest (6-7 mm.) is on the dorsal end and directed upward ; the next (5-6 mm.) is 

 on the middle of plate, directed outward or distad ; the third (3 mm.) is near lower end, 

 directed downward. Alternating with these (with some interruptions in regularity) are 

 diplacanthid plates ; the uppermost spine (subequal to the dorsal of triplacanthid plates) 

 is set slightly above middle spine of other plates, while the second (about two-thirds 

 length of upper) is opposite interval between middle and lower spine of triplacanthid 

 plates. The surface of plates has a sparse covering of very delicate ciliary spinelets which 

 become crowded on the transverse margins to cover the fascioles. There is an occasional 

 inferomarginal pedicellaria, similar to abactinal but larger; and smaller than the 

 actinal pedicellariae. 



The small actinal plates, in a single series, overlap the outer margin of the adambula- 

 crals and are so strongly joined to the inferomarginals that they appear to be the lower 

 ends of these plates. Each plate is subconical and carries at apex a prominent, lanceo- 

 late, two-jawed pedicellaria. 



