CLARK: BRITTLE-STARS. 327 



genus has been transferred to the Ophiocomidae, as first suggested by 

 Verrill. The discovery of a new species at the Tortugas makes it 

 desirable to pubHsh a key to those now known. I have found no 

 record of a species wrongly referred to the genus. 



Ophiopsila was proposed by Forbes, (1843. Trans. Linn. soc. 

 London, 19, p. 149) for a brittle-star from the Aegean Sea, which he 

 called Ophiopsila aranea. Some years later Sars (1857, Nyt. mag. 

 naturvid., 10, p. 23) described two species from the Mediterranean, 

 for which he proposed a genus Ophianoplus. He thought it was 

 distinct from Forbes's genus, because oral papillae were present and 

 radial shields seemed to be wanting. As a matter of fact however, 

 oral papillae and radial shields are present in both and it has been 

 agreed for many years that Sars's generic name is a synonym of 

 Ophiopsila. Of Sars's two species, one {marmoreus) has long been 

 recognized to be a synonym of Forbes's 0. aranea, while 0. annulosus 

 has been universally accepted as a valid species. It seems however, 

 that there is much evidence to show that 0. annulosa is simply full- 

 grown 0. arajiea. The only differences that have been suggested are 

 the smaller size and fewer, slenderer arm-spines of 0. aranea; but in 

 large specimens of 0. aranea (8 mm. across the disk) there are 8 arm- 

 spines, not at all slender, while Mangold (1907) figures an arm-seg- 

 ment of 0. aiinulosa with only 10 arm-spines. Even the work of 

 Mangold, Reichensperger, and Trojan on the phosphorescence of the 

 Mediterranean species of Ophiopsila confirms the view that 0. aranea 

 is the young and 0. annulosa the adult of a single species. Each 

 of these authors treats them as distinct, without however, careful 

 comparisons. In view of their distribution and all the other facts 

 that are known, it would seem the wo nominal European species 

 might well be considered as really only one, for which Forbes's name 

 would, of course, be used. One fact, however, weighs heavily against 

 this course; the uppermost arm-spines are not the smallest in 0. 

 aranea as they are in 0. annulosa and as they would naturally be if the 

 increased number were simply a growth-change. As I have seen no 

 specimens of 0. annulosa and find none recorded with fewer than 10 

 arm-spines, I let the two species stand as they have for sixty years. 

 An abundance of material will probably show they are identical. 



In 1859, Liitken described (Add. ad hist. Oph., pt. 2, p. 136) a 

 West Indian brittle-star, undoubtedly congeneric with 0. aranea; 

 it was taken at St. Thomas and was named 0. riisei, in honor of its 

 collector. Nearly twenty years passed before another member of the 

 genu3 was discovered. Lyman (1878. Bull. M. C. Z., 5, p. 227) then 



