1044 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
On outer attenuate part of ray they become much reduced in size. First superomarginal either lacks 
the spinule or bears a very small one. General surface of plates is covered with scattered, small, 
papilliform spinelets. 
Inferomarginals form a rounded and conspicuous border to actinal area, on which their length is 
greater than their breadth. They are slightly higher than the superior series. Each plate, on lateral 
face and near upper angle, bears a prominent, cylindrical, tapering, sharp spine, which stands out 
horizontally from ray. These spines are about 3 mm. long, and decrease in length at tip of ray. 
Below this are grouped 3 to 5 shorter and more delicate spinules, often in a rude semicircle, the longest 
being one-half to two-thirds the length of spine. On the inner plates of ray these accessory spinules 
are usually placed in an irregular transverse series, accompanied by numerous enlarged spinelets. 
Surface of plates is covered with spaced, usually sharp, papilliform spinelets. 
Adambulacral plates have an angular projection into furrow, the spiniferous rim being rounded to 
subangular. Greatest breadth is greater than length. Armature as follows: (1) A palmate furrow 
series of 7 slender, tapering, blunt spinelets, the 3 or 4 median subequal, or the median slightly the 
longest. (2) On actinal surface 1 conical, erect, pointed spine stands in center of plate. On outer part 
of ray a second smaller spinule is present in an oblique line toward inner aboral corner of plate. 
This spinule seems to be represented throughout rest of ray by a slender spinelet on the aboral border 
of plate. First 2 adambulacrals have a second smaller spine toward the furrow angle, but this does 
not appear to hold for all the rays of the type specimen. Three or 4 small spinelets stand in a row 
along adoral margin of plate, forming a continuation of furrow series. One or 2 similar spinelets are 
also occasionally found on outer end of plate near inferomarginals. 
Mouth plates prominent, broad, and the united pair strongly convex, with a wide semicircular 
free margin. Their interradial length about equals width of united pair. Each plate bears a marginal 
series of 8 spinelets, the 2 innermost enlarged into flattened, slender, slightly tapering spines, which 
project horizontally over the mouth and with those of the companion plate form 4 “teeth,” the 2 
median of which are a trifle the longest. The other marginal spines are about half the length of 
teeth, and diminish in size as they recede from them. On actinal surface of each plate is a linear 
series of numerous spinelets, running parallel to median suture, which decrease in size as they proceed 
outward. Between this series and lateral margin, and much nearer inner than outer end of plate, 
stands a single prominent spine similar to that which is found on the actinal surface of each adambula- 
cral. Numerous small miliary spinelets are found on outer half of each plate. 
Actinal interradial areas small. Intermediate plates 10 to 12, convex, armed with small, widely 
spaced, spinelets. Intermediate plates extend only as far as the fourth adambulacral, and usually not 
beyond third. 
Anal aperture nearly central, easily detected. 
Madreporic body small, subcircular, situated about midway between center of disk and margin, 
marked with coarse radiating striations. There is a large paxilla on its adcentral side. 
Color in life unknown; in alcohol ashy white, yellowish on arms. 
Variations: In a large mutilated specimen which appears to belong to this species the disk is rela- 
tively slightly larger, and interbrachial arcs more rounded. The papularium is more prominent also. 
Each adambulacral plate bears a second smaller spinule in an oblique line toward the outer adoral 
corner of plate. The inferomarginal plates are slightly broader on actinal surface than in type. It is 
barely possible this may represent another closely related species, but with the material at hand it is 
impossible to determine this. The species of Cheiraster are as a rule very variable. 
Localities: Type (no. 21157, U. S. National Museum) from station 3865, Pailolo Channel, between 
Molokai and Mauai, 256-283 fathoms, fine volcanic sand and rocks; bottom temperature 44. 8°. Station 
3868, same locality, 294-684 fathoms, fine gray sand and rocks. Cruise of 1891, 3474, south coast of 
Oahu, 375 fathoms, fine white sand; 8 specimens. 
This species can readily be distinguished from the preceding by the longer, slenderer rays, very 
much less spiny dorsal integument (the spinules being inconspicuous), and less spiny marginal plates. 
It-is apparently more nearly related to Ch. planeta, taken by the Challenger Expedition in 245 fathoms 
off the western coast of South America (near the entrance to the Straits of Magellan, opposite Port 
Churruca) than to any other known form. From planeta, inops would be readily distinguished by its 
relatively smaller disk, more attenuate, longer rays, more numerous papulae in the papularium, and 
by the considerably larger abactinal paxillae. The armature of the inferomarginal and adambulacra; 
plates also presents points of difference. 
