178 BULLETIN 100^ UNITED STATES NATIONAL MUSEUM. 



the plates bear 1 or 2 (rarely 3) two-jawed pedicellariae, similar to 

 the subambulacral and inferomarginal pedicellariae. The second 

 pedicellaria is usually considerably smaller than the other, which is 

 about as long as the transverse diameter of the plate. The plates 

 are armed also with 2 to 5, but sometimes upward of 10, very slender^ 

 fairly long, spinelets about as large as those of inferomarginal 

 plates. The pedicellariae are lacking in denudata. 



Except on the first 8 to 12 plates at base of ray, the characteristic 

 furrow pedicellaria of denudata occurs very rarely in the type, but 

 in specimens from stations 5402 and 5406 it occurs more frequently, 

 at least on some rays. At best its occurrence is sporadic. The 

 pedicellaria is very slender and resembles a compressed truncate 

 furrow spine, the thin jaws being oriented distal and proximal, or 

 at right angles to the pedicellaria of avicularia. It is about two- 

 thirds the length of the furrow spine. 



The adambulacral armature consists of a transverse series of 3 

 rather long spines, increasing in length outward, the inner 2 being 

 compressed. The outer is occasionally a little out of line, being 

 crowded by a large two- jawed slender pedicellaria on its proximal 

 side, or opposite the interval between the second aijd third spines. 

 One or tAvo small pedicellariae are usually found just adorad of the 

 above, while another is sometimes present just external to the outer- 

 most spine, along f^^ith 2 or 3 delicate spinelets. This outer pedi- 

 cellaria varies greatly in size. At the base of the ray the spines 

 are very compressed and form a vertical series between the tube feet, 

 the outer spine only being bent away. Here there are usually 2 or 

 3 large subambulacral pedicellariae, with several small ones at 

 their base. Also the proximal plates frequently have the furrow 

 pedicellaria. It resembles a supernumerary compressed bladelike 

 furrow spine below the regular spine. As in L. avicularia^ the 

 armature at the base of ray is variable and not typical of most of the 

 adambulacral plates. On the outer third or fourth of ray, or even 

 over a greater extent of the distal region, the subambulacral pedi- 

 cellariae are lacking, there being 3 spines in a transverse series, 

 with a few (2 or 3) slender spinelets standing just adorad of the 

 outer spine. The armature differs from that of denudata in lacking 

 usually the furrow pedicellaria, in having the second spine strongly 

 compressed, not terete, and in having a characteristic pedicellaria 

 adorad of the third spine, or the second and third, in addition to 

 1 or more smaller accessory pedicellariae. In denudata the only 

 subambulacral pedicellaria is situated external to the external spine, 

 where, in yymnochora, a small or medium-sized pedicellaria is often 

 present. 



The armature of the mouth i)latcs consists of (1) a superficial 

 series bordering the median suture, consisting of 8 to 12 spines and 



