88 DISCOVERY REPORTS 



species of Rosacea, referred to by Bigelow as R. medusa Metchnikoff (1870), belongs to a separate 

 genus. I have re-examined the Russian 1 account and figures of Metchnikoff, and repeat some points 

 of interest referred to in his Russian description. 



Praya medusa is described as being the most transparent of siphonophores, and is very difficult to 

 catch. It differs from P. diphyes Vogt, says Metchnikoff, in its smaller size, shape, as figured by him, 

 and equality of development of the nectophores, which do not overlap as in P. maxima. There is less 

 gelatinous substance and there is a wide velum. Most important is the mention of little tentacles and 

 ' eye-spots ' on the edge of the nectophores as well as on the edge of the special nectophores of the 

 eudoxids, in the latter of which they number from twenty-five to thirty. Metchnikoff does not mention 

 or figure the four radial subumbral canals of the main nectophores but says that the vascular system 

 is 'the same as in other species '. There is a single (pallial) vessel running from top to base and ending 

 in a small vesicle (somatocyst). The shape of the comparatively small gonophores can be seen in 

 Metchnikoff's figures. Since this species was recorded from the Mediterranean, with whose fauna 

 most of the siphonophore pioneers dealt, it may be useful to give my conclusions about the identity 

 of the various Prayids found in the Mediterranean. 



There appear to be at least six species belonging to four genera in the Mediterranean : 



Genus A. Rosacea (Q. & G.) Bigelow, 191 \b 

 Species 1. R. cymbiformis Delle Chiaje, 1822. 

 Species 2. R. plicata ([?] Q. & G.) Bigelow, 191 ib. 



Genus B (new name required). ?= Desmophyes Haeckel, 1888 a 



(A pyriform branch of the eudoxid's somatocyst present.) 



Species 3. Praya diphyes Kolliker, 1853 ft. 



Diphyes Brajae [sic] Vogt, 1851. 



Praya diphyes Vogt, 1854 not pi. 16, fig. 3 =R. cymbiformis). 



Praya diphyes Graeffe, i860 (Taf. I, fig. 2). 



Praya diphyes Fewkes, 1880 (pi. ill, fig. 1). 



Praya fill 'for mis Keferstein & Ehlers, 1861 (pi. v, figs. 8-1 1). 



Genus C. Lilyopsis Chun, 1885 

 Species 4. Lilyopsis rosea Chun, 1885 (with meandering lateral canals in (main) nectophores). 



Praya diphyes Graeffe, i860 (Taf. I, figs. 1 a, b, c; eudoxids). 

 Lilyopsis diphyes Moser, 1917, 19246. 

 ? Praya medusa Metchnikoff, 1870. 



Species 5. Lilyopsis sp. (Fewkes), 1880 (pi. ill, fig. 2) (with straight lateral canals in (main) necto- 

 phores). 



Genus D. Stephanophyes Chun, 1891 



Species 6. Stephanophyes superba Chun, 1891. 



Forms closely resembling species 3 (as ' Rosacea plicata ') and 6 are recorded also from Misaki by 

 Kawamura 2 (191 5); species 4 by Bedot (1896) from Amboina; and species 6 from the Canaries by 

 Chun (1891). 



In the course of many years during which I have been searching plankton samples for Siphonophora, 

 I have found outside the Mediterranean — in the Atlantic, Indian and Antarctic Seas — many Rosacean 



1 I have to thank Dr S. B. Markowski for translating parts of Metchnikoff's paper. 



2 I have to thank Dr Mary Sears for having been instrumental in producing a valuable translation by Rodney Notomi of 

 most of Kawamura's inaccessible Japanese work. 



