CLARK: AUSTRALIAN AND INDO-PACIFIC ECHINODEEMS. Ill 



LINCKIIDAB. 



Hacelia helicostichus. 



" Linclia nodosa Perrier " Bell, 1884. " Alert " Rept., p. 124. 



Ophidiaster helicostichus Sladen, 1889. " Challenger " Ast., p. 405, pi. 69, figs. 5-7. 



Among the starfishes received in. exchange from the British Museum, in 1907, 

 is a handsome specimen labelled " Linckia nodosa.''' It is from Prince of Wales 

 Channel, Torres Strait, 7 fms., was collected by the " Alert," and has the rays 

 118 mm. long. It must be therefore one of those referred to by Bell (1. c.) in the 

 " Alert " Report. Comparison with a specimen of L. nodosa of about the same 

 size, labelled by Perrier, shows, what a careful reading of Perrier's description 

 clearly indicates, that the two species are not even congeneric. The Torres 

 Strait specimen is evidently a fine example of Sladen's Ophidiaster helicostichus, 

 which was taken by the " Challenger " in Torres Strait. Our specimen has the 

 rays wider at the base than is shown in Sladen's figure, but otherwise shows no 

 peculiarities. The tips of the rays have a bluish tinge which may indicate that 

 the species in life is blue, like Linckia laevigata. There can be no question, 

 I think, that this species is congeneric with Hacelia attenuata Gray of the 

 Mediterranean. 



OPHIUROIDEA. 



OPHIODERMATIDAE. 



The Genera Ophiarachna s. lat. and Ophiopeza. 



The genus Ophiarachna Miiller and Troschel was established in 1842 with four 

 species, one of which (0. incrassata Lamk.) was readily distinguishable from the 

 others (0. gorgonia, 0. infernalis, and 0. septemspinosa) by its few, long, stout 

 arm-spines and concealed radial shields. The same year the genus Pectinura was 

 established by Forbes for a very small ophiuran (P. vestita) from the iEgean Sea, 

 which would naturally have gone in Ophiarachna had Forbes known of the exist- 

 ence of that genns. In 1851 Peters established Ophiopeza for a species (0. 

 fallax) from Mozambique, distinguished from Ophiarachna and Pectinura by the 

 lack of supplementary oral plates. In 1856 Lutken described a second species 

 of Ophiopeza (0. yoldii) which he subsequently made the type of a new genus, 

 Ophiopsammus. Ten years later Ljungman described two new Ophiarachnas, 

 one (0. spinosa) from Fua, Tonga Islands, the other (0. stellatd) from Singa- 

 pore. The next year Grube redescribed the latter under the name Ophiolepis 

 (Ophiochasma) adspersa. In 1869 Lutken made the first attempt at a revision of 

 the group, removing from Ophiarachna 0. gorgonia, 0. infernalis, and 0. septem- 

 spinosa, leaving 0. incrassata as type of the genus and adding a new species 

 (0. affinis) thereto. He went still further and separated Ophiarachna from its 

 former ally, Pectinura, to which he had added several species, and associated it 

 with Ophiocoma instead. He refers to the fact that the character which was sup- 



