176 BULLETIN 100, UXITED STATES NATIONAL MUSEUM. 



row pedicellaria beyond a few j)lates at base of ray, except rarely 

 and sporadically; second furrow spine compressed; several sub- 

 ambulacral pedicellariae, the principal one situated adorad of the 

 second and third spine; rays 11. R=230 mm., r=33 mm.; breadth 

 of ray at base 22 mm., a short distance beyond base 28 mm.; rays 

 deciduous and usually imperfect, the tips being in the process of 

 regeneration or absent; many rays are broken into 2 or 3 pieces: 

 rays thin, plane, with very widely open, shallow ambulacral fur- 

 rows; tube feet long, sometimes reaching to the margin, and with 

 a small conical button at tip ; skeleton loose, dorsal integument thin. 



Description. — Paxillae of disk rather more closely placed (espe- 

 cially in the middle) than on v?iys. Each consists of a rather slender 

 shaft (slenderest at the middle) surmounted by a circle of 8 to 12 

 very slender, sharp spinelets, about as long as the shaft, and sur- 

 rounding a large central two-jawed tapering pedicellaria, Avhich is a 

 little longer than the spinelets. Seen from the side the pedicellaria 

 is about 2 to 2.5 times as long as the width of the base. The joints 

 are nearly of an equal width the whole length, or they taper slightly, 

 or are very narrowly spatulate. Below the base of the spinelets fas- 

 tened to the side of the shaft are 1 to 5 delicate, slender, blunt, two- 

 jawed pedicellariae from one-half to two-thirds the length of the 

 spinelets, and frequently oriented at uight angles to the shaft. In 

 the type nearly all the paxillae of the disk have the large central 

 pedicellaria. They are not so numerous in a young specimen. 

 The pedicellariae are entirely lacking in L. denudata. 



On either side of the rays there are 3 regular series of large 

 paxillae, the outer series of which represents the superomarginals. 

 Over the median part of the ray the paxillae are smaller and ar- 

 ranged without definite order. Nearly all the paxillae have the 

 pedicellariae described above, except in the case of regenerating tips, 

 where they are much less common. On the outer half of the ray 

 the central pedicellaria of the 3 regular series is replaced by a slender, 

 sharp spine. This usually remains small on the median series, but 

 increases in size on the other 2 series as the end of the ray is ap- 

 proached. It augments in size more rapidly on the inner series 

 and attains a length of 5 to 10 times the height of the here much- 

 shortened pedicels. These distal spinopaxillae are quite constant, 

 although occasionally a paxilla will lack a spine, or the length of 

 the spines will vary. Many of the other paxillae of the distal fourth 

 of the ray have the pedicellaria replaced by a spine, but the latter 

 does not surpass the other spinelets enough to become conspicuous. 

 These spinopaxillae are not present in denudata. 



The regular paxillae have regularly four-lobed or cruciform bases, 

 the transverse lobes being longer than the longitudinal ones (the 



