REPORT ON THE ASTEROIDEA. 407 



half of its margin are more papilliform than the other granules on the abactinal plates 

 generally. 



The anal aperture is small and exceutric in position, and is surrounded by a number 

 of small scutiform papillae, which trend over the orifice. 



The primary apical plates are very conspicuous. 



Colour in alcohol, a brownish white, mottled with patches on the abactinal area of a 

 light chocolate colour. All the papular areas are a dark greyish brown. This distribution 

 of colour produces a very ornate appearance. The actinal surface is yellowish white. 



Locality. — Station 187. Booby Island, Torres Strait. September 9, 1874. Lat. 10° 

 36' 0" S., long. 141° 55' 0" E. Depth 6 fathoms. Coral mud. Surface temperature 

 77° 7 Fahr. 



Remarks. — This large and elegant form is distinct from any other species with which 

 I am acquainted. It resembles in some of its details Ophidiaster tuberifer, but is readily 

 distinguished by the larger size, the tapering rays, the absence of tubercles on the 

 abactinal plates, the small size of the granulation on the abactinal plates, the peculiar 

 character and disposition of the granulation of the papular areas, the difference in the 

 adambulacral armature (which in Ophidiaster hclicostichus is in two series, whereas in 

 Ophidiaster tuberifer three series are present), and in the presence of the large-bossed 

 pedicellarite. The pedicellarise generally are, if anything, smaller in the species under 

 notice than in Ophidiaster tuberifer. 



Genus Leiaster, Peters. 



Leiaster (subgen.), Peters, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, April 1852, p. 177. 

 Lepidaster, Verrill, Trans. Conn. Acad. Arts and Sci., 1871, voL i. part 2, p. 577 (non Lepidaster, Forbes, 



1850). 

 Ophidiaster (pars), Perrier, Revis. Stell. Mus., p. 121 (Archives de Zool. exper., 1875, t. iv. p. 3^5). 



This small group of species, although distinctly allied to Ophidiaster, appears to me 



worthy of generic recognition. The soft thick skin with which they are covered causes 



them to have a gelatinous or slimy character to the touch when alive, and this together 



with minor differences of structure produces a fades altogether different from that 



of any of the species of true Ophidiaster. Von Martens 1 and de Loriol 2 have both 



expressed the same opinion. Leiaster, as at present known, is confined to the Indian Ocean, 



the Eastern Archipelago, and the Pacific, and appears to be local in its occurrences. 



Chorology of the Genus Leiaster. 

 a. Geographical distribution : — 



Indian Ocean : Three species between the parallels of 10° and 30° S. 



Leiaster coriaccus and Leiaster glaber, from Querimba Island. 

 Leiaster coriaceus and Leiaster leachii, from Mauritius. 



1 Archiv f. Naturgesch., Jahrg. xxxii., Ed. i. p. 71. 



2 Mem. Sue. phys. hist. nat. Geneve, t. xxix. p. 40. 



