CLARK: BRITTLE-STARS. 305 



have in 0. abyssicola, as in-0. plana (probably), a cosmopolitan, deep- 

 water Ophiactis, known as yet however only from the north and 

 south Atlantic and from the Pacific near the Kermadec Islands, in 

 64-945 fms. 



Ophiactis canotia. 



Lyman, 1879. Bull. M. C. Z., 6, p. 38. 1882. Challenger Oph., pi. 19, 

 fig. 16-18. 



The only known locality for this species is near the Azores Islands 

 at a depth of 1,000 fms. 



Ophiactis loricata. 



Lyman, 1869. Bull. M. C. Z., 1, p. 331. H. L. Clark, 1915. Mem. M. C. Z., 

 25, pi. 10, fig. 3, 4. 



This interesting little species is known as yet only from near Alligator 

 Reef, Florida, in 110 fms. The upper arm-plates are quite different 

 from those of any other Ophiactis even when very young specimens 

 are used for comparison. 



Ophiactis savignyi. 



Ophiolepis savignyi Miiller and Troschel, 1842. Syst. Ast., p. 95. 



Ophiactis savignyi Ljungman, 1867. Ofv. Kongl. vet.-akad. Forh. 23, p. 323. 



Ophiactis krebsii Liitken, 1856. Vid. med., p. 12. 



Ophiactis virescens Liitken, 1856. Vid. med., p. 24. 



Ophiolepis sexradia Grube, 1857. Arch. f. naturg., 23, 1, p. 343. 



Ophiactis reinhardtii Liitken, 1859. Add. ad hist. Oph., pt. 2, p. 161, pi. 3, 



fig. 7a, 6. 

 Ophiactis incisa von Martens, 1870. Arch. f. naturg., 36, 1, p. 248. 

 Ophiactis brocki de Loriol, 1893. Rev. Suisse zooL, 1, p. 401. 



The diversity of characters shown by this tropicopolitan species is 

 not very extraordinary but growth-changes are considerable and the 

 customary multiplication by fission causes many superficial differences. 

 There is no doubt, however, that the multiplicity of names is due more 

 to its unusually extensive range than to differences of structure. The 

 characters by which it may be recognized have been given above in 

 the key but it may be added that the number of arms is typically 

 5 or 6, though individuals with 4 or 7 are by no means rare. The 

 species occurs most abundantly in the cavities of sponges in very 



