Fauna Associated with Crinoids of Tropical Coral Reef, etc. 



91 



ECHINODERMS. 



The only echinoderms which were found associated with the crinoids 

 were ophiurans, and of these only one genus (Ophiomaza) is charac- 

 teristically commensal. A small species of Ophiactis, which seems 

 to be as yet undescribed, and a young Ophiocoma, too small for accu- 

 rate determination, were found on Comanthus annulatum, but it was 

 not possible to determine whether this association was anything more 

 than accidental. But of Ophiomaza a sufficient number of specimens 

 was found to show that that genus is normally commensal. All the 

 individuals taken were on comatulids; none were seen elsewhere. On 

 Comanthus annulatum were found specimens of Ophiomaza cacaotica, 

 uniformly black (or very deep purple or brown) ; 0. cacaotica var. picta, 

 prettily marked with black and white; and 0. obscura, brown, hand- 

 somely marked with dull yellow. In all these cases, a certain amount 

 of correlation between the colour of the ophiuran and the colour of the 

 host was obvious. But on a bright red Comatula purpurea was found 

 a small black specimen of 0. cacaotica, and of course the colour contrast 

 was very striking. However, Ophiomaza was much too rare to permit 

 any reliable deductions to be drawn concerning the influence of com- 

 mensalism on the colouration. 



POLYCH^ETA. 

 Polynoe minuta Potts var. oculata var. n. 



This polychsete, which I found rather frequently on the darker vari- 

 eties of Comanthus annulatum, undoubtedly comes nearest to Polynoe ? 

 minuta, which I described in 1910 from specimens collected by Professor 

 J. Stanley Gardiner in the Maldives.* It was not stated that this form 



l\ ' 



\ ^' 



FIG. 7. Polynoe minuta Potts var. oculata var. n. 



A. Head and anterior part of dorsuni to show colour pattern; median tentacle, 



tentacular cirri, and dorsal cirri all wanting. X8. 



B. Seta?, a, dorsal; b-e, ventral. 



C. Parapodium of sixth segment. X65. 

 References in text: A, B, C, X163; D, E, X280. 



occurred upon crinoids, although the labels of the various specimens of 

 P. crinoidicola, in the same collection, gave quite definite information 



*Trans. Linn. Soc., London, vol. xm, pt. 2, Polychseta of the Indian Ocean; pt. n, The 

 Palmyridse, Aphroditidse, Acostidse, and Sigalionidse. See p. 337. 



