﻿OPHIURA RUBICUNDA. 3X 



small, oval, length I"""- ; 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 tapering, rounded 

 at end ; rest of spines more flattened, short, and tapering, increasing 

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

 arm-plate : first sjaine, .9 : 1.2 ; second spine, .8 : 1.2 ; fifth spine, .6 : 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 and 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 



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 0. rubicunda. The mouth-shields are as in O. cinerea, 

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

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

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

 had a disk of 20"'°, whUe 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 hybrid between 0. rubicunda and 0. cinerea. 

 No hybrids occur between the other closely allied West Indian Ophiu- 

 rans. Among many hundred specimens of Ojjhiocoma crassisj^lna and 

 O. Biisei that I have exammed, 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 improbable that it may prove a new 

 species. 



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

 and whole upper arm-plates, and, by the latter character, from O. squct- 

 mosissima ; from 0. panamensis, by larger mouth-shields, naked side 

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



