OPHIURA RUBICUNDA. 3I 



snicall, oval, length !"""• ; there are sometimes, near base of arms, above, 

 one or two little naked rounded plates. Arm-spines eight or nine, low- 

 est one much longest and largest ; flattened, shghtly tai)ering, rounded 

 at end ; rest of spines more Hattened, short, and tapering, increasin*-- 

 gradually in length from above downward ; lengths to that of lower 

 ann-plate : first spine, .9 : 1.2 ; second spine, .8 : l.'i ; fifth spine, .(J : 1.2 ; 

 ninth spine, .5:1.2. About two thirds out on arm, only six spines, 

 which are sharp and rounded. Tentacle-scales, inside one clean oval, 

 rather thin ; length to that of under arm-plate, .7 : 1.2 ; outside one 

 shorter, rather broader, cut square off at the end. Color, in alcohol : 

 above, disk uniform dull pink-red (lake and Indian red), arms finely 

 and irregularly mottled ;md banded with lighter and darker shades 

 of the same ; below, uniform in color, which is the same as that 

 above, but much lighter; arms somewhat lighter than interbrachial 

 spaces. 



Variations. — Another specimen was somewhat darker than the 

 above, had the disk finely mottled, and the arms mottled, red and light 

 yellowish. The arms are usually, in well-grown specimens, about five 

 times the diameter of the disk. There is a so-called variety of this 

 species, which may be said to have the under side of 0. cinerea, and 

 the upper side of O. rubicunda. The mouth-shields are as in O. cinei^ea, 

 and the mouth-papillae, though finer and more irregular, are also some- 

 what alike ; the mouth-shields are surrounded by granulation, which 

 completely covers the side mouth-shields. The specimen I examined 

 had a disk of 20°"" , while the length of the arms was only four times as 

 great. It is manifestly not philosophical to suppose, as Dr. Liitken 

 does, that this form is a hylwid between 0. riihlcunda and 0. cinerea. 

 No hybrids occur between the other closely allied West Indian Oj^hiu- 

 rans. Among many hundred specimens of Ophlocoma erassisjnna and 

 0. R'dsei that I have examined, I never saw one that even looked like 

 a hybrid ; and the same is true of other species. This form is certainly 

 a curious one ; and it seems not imj)robable that it may prove a new 

 species. 



O. ruhicunda is distinguished from 0. cinerea by smaller radial-shields 

 and Avliole upper arm-plates, and, by the latter character, from O. sqita- 

 mosissima ; from 0. 2)cmamensls, by larger mouth-shields, naked side 

 mouth-shields, outer mouth-papilla3 broader, &c. 



