92 BULLETIN 100^ UNITED STATES NATIONAL MUSEUM. 



sometimes as mentioned above, more or less compressed, so as to be 

 elliptical in cross-section. In the type the paxillae of the disk are 

 about 3 mm. high, including the tuft of cylindrical spinelets, which 

 vary from slightly shorter to slightly longer than the pedicel. In a 

 specimen from station 5392 the pedicels on the disk, except near 

 the extreme margin, are longer than the spinelets. The larger 

 jDaxillae of the disk have 10 to 15 subequal, blunt, slender spinelets, 

 usually standing erect in a compact group ; when dried the spinelets 

 become sharper. 



The plates of the papular area have a very characteristic form, 

 which may be described as 4-lobed, the 2 lobes on the axis of the 

 oblique transverse series being pointed, while the other 2 lobes are 

 considerably broader and truncate. The plates do not touch, except 

 sometimes near the margin, and most of them have a slight sub- 

 conical or keellike elevation near or at the center. There are 6 

 papulae around each plate. Along a median radial area (about half 

 as wide as either lateral papular area) and the center of disk the 

 plates are irregularly subcircular to broadly elliptical and 1.5 to 

 2 times as broad as the lobed plates. This area is free from papulae, 

 and the plates are spaced one-half to a little more than their own 

 diameter. In C. ludioigi the plates of the papular area are only 

 slightly or not at all lobed. The lobes are best marked on the outer 

 part of the ray, the plates of the proximal portion being subcircular, 

 with indications of 4 to 6 scallops on the margin. 



Superomarginal plates, 48 or 49 in type, former much as in A. 

 ludwigi, with a broad dorsal face passing by an abrupt rounded angle 

 into the lateral face, which is about half the width of the dorsal. 

 The exposed surface of the plate is decidedly convex along the me- 

 dian transverse line, this fact and the armature giving the species 

 somewhat the appearance of a Persephonaster. The marginal area 

 of the plate is covered w^ith delicate, blunt, closely placed spinelets, 

 which decrease in length toward the median transverse area, where 

 the armature is in the form of coarse, rounded granules, which in- 

 crease in size from the inner edge of the plate toward the lateral 

 angle of the ray, these becoming more or less conical and sometimes 

 squamiform around the base of 2 to 4 short, conical, stout spinules 

 which form a transverse series or a group. These correspond 

 to the superomarginal spines of Z. ludwigi, but are more closely 

 bunched on the margin of the ray. Sometimes a smaller, thick, 

 granuliform, conical spinolet is found spaced from the others toward 

 the inner margin of the plate, or a line of two or three such, espe- 

 cially on the second to fourth plates. The first plate lacks spines. 

 On the outer third of the ray the granules cover most of the exposed 

 surface, but as the middle of the ray is gpproached the granular area 

 becomes narrower and the plates slightly more tumid. The last 4 



