486 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



tudinal series, the plates of which also form regular vertical series, 

 •which correspond fairly regularly to the adradial plates. The 2 

 upper series represent the marginals, which are larger than the 

 plates of the 4 inferior rows, the superomarginals being slightly 

 smaller than the smaller adradial plates, and the inferomarginals a 

 trifle smaller than the superomarginals. A series of tiny papulae 

 is present between the adradial and superomarginal plates, another 

 between the marginals, a third below the marginals (not complete) 

 and a fourth, very incomplete, between the first 2 intermediate rows. 

 Each carinal and adradial plate bears a sharp, appressed, lanceolate 

 spine similar to those of disk, and forming 3 series along the dorsal 

 surface of ray, the outer series being on the margin between the 

 dorsal and lateral faces of the ray. On the distal adradial plates 

 the spinelets are arranged in 2 transverse series, and on the last 25 

 in a single series. The marginal plates bear each a slender, needle- 

 like spine, that of the inferomarginals being proximally one and a 

 half or two times the length of the superomarginal or about 3 mm. 

 This spine increases in length to about 5 mm. along the middle 

 third of the ray, then decreases, while the superomarginal spine 

 remains 1.5 to 2 mm. long until near the end. Each of the interme- 

 diate plates bears a large flattened, slender, sharp, appressed spine 

 borne on a prominent boss which occupies most of the available sur- 

 face of the plate. The spines are arranged thus in vertical series of 

 4 proximally and 3 distally; the upper is 5 to 5.5 mm. long, the 

 next subequal or a little shorter (especially distally) ; the third, 3.5 

 to 4 mm., and much slenderer, while the lowermost is about 3 mm., 

 and still slenderer. These spines which are in line with the margi- 

 nal spines form a dense armature all along the side of the ray. Two 

 or 3 short, stout pedicellariae a trifle shorter than the spinelets guard 

 the dorsal papulae, while usually 1, but occasionally 2, occur close 

 to the lateral papulae of the 2 upper series. The lower row of these 

 2 extends only a short distance along ray. 



Prominent adambulacral plates have a single series of 3 slender 

 spines directed into the furrow, the middle the longest ; on the actinal 

 surface are 1 or 2 spines (similar to the foregoing, and in line with 

 them) and 3 shorter spinelets, the 4 or 5 forming 2 transverse series. 

 The innermost furrow spine has 1 to 4 pedicellariae at the tip, the 

 largest about one-half to three-fourths the length of the spine. Non- 

 prominent plates with 4 spinelets surrounding a subcentral spine. A 

 spinelet on the furrow margin carries 1 or 2 small pedicellariae. The 

 inner furrow spine of the first 4 or 5 plates has numerous pedicellariae, 

 while those on the mouth plates proper have upward of 40. These 

 form a circle surrounding the mouth, the clusters touching one an- 

 other. Tube feet in 4 series for three-fourths the length of ray. 



