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



The family Salacidae is an interesting group intermediate between two very 

 dissimilar families of Cystonectse, the macrostelious Rkizophysidse (XXI.) and the brachy- 

 stelious Pkysalidse (XXIV.). It agrees with the former in the long tubular stem and the 

 long naked internodes between the ordinate cormidia, and further in the peculiar 

 structure of the pneumatophore, possessing hypocystic villi ; on the other hand, it agrees 

 with the Physalidae (PI. XXVI.) in the polygastric structure of the cormidia and the 

 large size of the float, and with Physalia especially in the structure of the siphons and 

 the simple tentacles, bearing a series of reniform cnidonodes. 



The remarkable species which represents this connecting family is figured in PI. 

 XXV. as Salacia polygastrica ; it was taken by the Challenger in the Tropical Atlantic 

 (Station 338), from a dej^th of 1990 fathoms. The single specimen examined was so well 

 preserved that it was possible by staining and dissecting it to recognise the essential 

 structure of all the different organs. The morphological relation which the polygastric 

 cormidia of Salacidse bear to the closely allied monogastric cormidia of Rhizophysidse 

 is very similar to that which, among the Physonectse, the Apolemidse bear to the 

 Agalrnidse. An Apolemia which has lost its nectophores and bracts would be very 

 similar to a Salacia. The peculiar structure of the gonodendra, however, in this latter, 

 and the structure of the large float, with eight radial bunches of hypocystic villi, leaves 

 no doubt that they are most closely allied to the Rhizophysidse. 



Genus 72. Salacia, 1 Haeckel, 1888. 

 Salacia, HkL, System der Siphonophoren, p. 45. 



Definition. — Salacidse with ordinate cormidia, each of which is composed of several 

 siphons and monostylic gonodendra. The single tentacle, which arises from the base of 

 each siphon, is a long simple tube, beset with a series of reniform cnidocysts. 



The genus Salacia was established by Linnd in 1746 for that very large Cystonect 

 which was called Physalia by Lamarck in 1816 (compare 1, p. 158 ; 79, p. 24). 

 Since the latter name is generally accepted, and the former (although seventy years 

 older) entirely forgotten, I employ it for this new genus, instead of giving a new 

 name. The characters of the genus Salacia, as the only known type of Salacidae, are the 

 same as described above for that family. As a peculiar character of the genus may be 

 pointed out the shape of the tentacles, which agree with those of Physalia. The species 

 described in the sequel (PI. XXV.) was discovered by the Challenger in the depths of 

 the Tropical Atlantic (Station 338). Another species of the same genus seems to be 

 the (incompletely known) North Atlantic form, which Fewkes described in 1886 as 

 Rhizophysa uvaria (45, part xii. p. 967, pi. x. fig. 6). 



1 Salacia, name of a sea-goddess, wife of Okeanos. 



