REPORT ON THE SIPHONOPHOR^E. 329 



Genus 71. Rhizojrfiysa, 1 Peron et Lesueur, 1807. 

 Rhizophysa, Peron et Lesueur, 14, Voyage aux terres australes. 



Definition. — Rhizophysidae with loose cormidia, the gonostyles being attached to the 

 internodes of the stem, between the siphons. Tentacles branched; tentilla polymor- 

 phous, partly simple, partly branched. 



The genus Rhizophysa is the oldest known form of Rhizophysidae, its Mediterranean 

 type having been described as early as 1775, by Forskal, under the name Physophorafili- 

 formis (11, p. 120, Tab. xxxiii. fig. F). Peron afterwards, in 1807, figured a similar form, 

 observed in the Atlantic, under the name Rhizophysa planostoma (14, pi. xxix. fig. 3). 

 Although this latter figure is very incomplete, it may be that it is identical with a 

 similar Rhizophysa, a single specimen of which I captured in December 1866, in the 

 Canary Island Lanzerote. The structure of this Atlantic species, for which I retain 

 Peron's name, was very similar to that of the well-known Mediterranean form, the best 

 description of which was published in 1854 by Gegenbaur (7, p. 324, Taf. xviii. figs. 

 5-11). The Atlantic Rhizophysa p>lanostoma differed, however, in the peculiar coloration 

 (the pneurnatophore, the stem, and the tentacles being rose-coloured, the siphons violet), 

 and in the special form of the tentilla; the majority of these were trifid, with an odd 

 median club and two paired lateral horns (similar to those of Cannophysa murrayana), 

 but scattered between them was a number of very large palmate tentilla, differing 

 from those figured by Gegenbaur (loc. cit., fig. 8) mainly by a large purple ocellus on the 

 convex outside ; the peculiar calcarate tentilla, which Gegenbaur compared with a bird's 

 head in the Mediterranean Rhizophysa filiformis (loc. cit., fig. 9), were absent. Compare 

 also Fewkes (41, pi. ii.). A third species of the true Rhizophysa, different from the two 

 former, is described by Brandt as Epibulia mertmsvi (25, p. 33). The excellent figure of it, 

 drawn from nature by Mertens (but unfortunately not published), exhibits distinctly two 

 different kinds of branched tentilla; the colour of the corm is yellowish-brown, the 

 siphons rose. It was observed in the Northern Pacific in 1827. 



Family XXII. S a l a c i d m, Haeckel, 1888. 



Salacklw, Hkl., System der Siphonophoren, p. 45. 



Definition. — Cystonectae polygastricae with a long tubular trunk of the siphosome, 

 bearing in its ventral median line numerous polygastric cormidia, separated by free 

 internodes. Each clustered cormidium composed of several siphons and several 

 tentacles. Pneumatosaccus large, without radial septa and pericystic radial pouches, 

 but with eight or more radial groups of hypocystic villi. 



1 .R/i»zop%sa = Root-bladder, pl^u, tpiasc. 

 (zoou CHALL. EXP. PABT LXXVII. — 1888.) Hhhh 42 



