6 THE VOYAGE OF H.M.S. CHALLENGER. 



47. Myzostoma cornutum, Graff. 



On Antedon alternata, P. H. C, from Station 236, Challenger Expedition, there was 

 found a dirty yellow translucent specimen of a small Myzostoma with damaged posterior 

 extremity, but agreeing in the character of its cirri, suckers, and parapodia with Myzo- 

 stoma cornutum (Das Genus Myzostoma, Taf. x.). It was apj)arently a very young form, 

 only 1 "2 mm. in length, and the difference in age may also account for the almost circular 

 outline of the body. Antedon alternata is a new host for this species. 



49. Myzostoma Jissum, Graff (PL I. figs. 5, 6). 



From two additional specimens of the above species I am now able to amplify my 

 previous description, which was based on a much contracted form. 



Both these new specimens measured, including the caudal appendages, about 4 '5 mm. 

 in length, and were of a yellowish-brown colour. On the one (figs. 5, 6) the first and 

 second pair of caudal appendages (I, II) were considerably shorter than the third, 

 and the dorsal ridge exhibited a sharp edge, and a less wavy outline than the specimen 

 figured in the Pieport (pi. iv.). The other specimen occupied, as regards its caudal 

 appendages, a median position between the two forms above mentioned, and the dorsal 

 ridge was only slightly defined. 



In both, however, it was distinctly seen that the figure of the ridges given in the 

 Report was doubly at fault. In the first place the ridges have a radial course on the 

 disc, the anterior running forwards, the posterior backwards to the margin ; and secondly, 

 similar ribs extend also from the body disc to the dorsal surface of the caudal 

 appendages. 



The figures show the ventral surface and exhibit the position of the mouth (m), the 

 strong parapodia (p), and the very slightly developed suctorial pits {s). 



These specimens were found lying loose in spirit with Antedon occulta, Antedon similis, 

 and Antedon tuhercidata, all new species from Station 174, Challenger Expedition, to the 

 south-west of Fiji. 



51. Myzostoma quadrijilum, Graff. 



This specimen was found on Antedon microdiscus. Bell, from Station 186, Challenger 

 Expedition, off Cape York. It was dark brown in colour, and measured, without caudal 

 appendages, O'S mm. in length and 0*64 in breadth, like the form represented in the 

 Report on pi. iv. fig. 3. There is, however, this difference between the two, that in this 

 form the external caudal appendages are much more strongly developed than the inner paii'. 

 They are as long as the body ; the thick basal portion measuring O'S mm., and the terminal 



