REPORT ON THE MYZOSTOMIDA. 7 



filament 0"3 mm. in length. Here again the cirri of the Jirst pair are the longest (0'2 mm.), 

 the others measuring only about 0'12 mm. Since the species exhibits manifold variations 

 (see Report, pp. 56, 57), I do not regard these differences as suflBcient for the establish- 

 ment of a new species. 



Antedon microdiscus is a new host for this Myzostoma. 



Another specimen, from Antedon hidentata, P. H. C, from Station 186 (Cape York), 

 Challenger Expedition, exactly resembled in form that figured in the Eeport, pi. iv. 

 fig. 4. The body was 0"8 mm. in length, and outside the base of the third pair of .feet 

 the slightly raised male genital papilla was very distinctly recognisable. 



52. Myzostoma qiiadricaudatum, Graft'. 



A specimen from Antedon Jluctuans, P. H. C, dredged in the Torres Strait from a 

 depth of 10 fathoms by H.M.S. "Alert." The body measured 0"83 mm. in length up to 

 the bifurcation, the maximum breadth was 078 mm., and the length of the largest caudal 

 appendage was 0*44 mm., the two posterior being slightly unequal. 



54. Myzostoma hicaudatum, Graff. 



Myxostoma hieaudahim, Graff, Bull. JIus. Comp. Zodl. Cambridge, vol xi. p. 1.31, 1883. 



55. Myzostoma filicauda, Graff. 



Myxostoma filiemida, Graff, Ihvl,, p. 132. 



57. Myzostoma carinatum, Graff. 



Myzostoma carinatum, Graff, Ibid., p. 131, 



In a vessel containiug Actinometra Solaris, Actinometra hennetti and five sjsecies of 

 Antedon from the Moluccas (collection of the K. zool. Genootschap, Amsterdam), there was 

 a Myzostoma, 2 '8 mm. in length, with lateral margins much folded towards the ventral 

 surface, but closely resembling Myzostoma carinatum (Eeport, pi. ii.) both in colour and 

 in the dorsal markings. The cirri, which occur very abundantly on the margin, are 

 relatively shorter and thicker, and have a maximum length of 0'2 mm. The median 

 dorsal ridge is especially prominent, and the paired laterals are less wavy than in the 

 above form, and start with their full breadth from the median pad instead of beginning 

 as fine ridges and becoming gradually broader. These differences are not however 

 sufficient for specific distinction. 



