HYDROZOA (HYDROID ZOOPHYTES AND 

 STYLASTERINA). 



By James Ritchie, M.A., B.Sc, The Royal Scottish 

 Museum, Edinburgh. 



(Plates Ixxxiv.-lxxxix., and fig. 126.) 



Despite the fact that Hydroid Zoophytes were obtained by the 



"Thetis" at only eleven of the fifty-nine definite stations at 

 which dredgings were made, the collection is one of great variety 



'and of much interest. Most striking in a general survey of the 

 collection, is the liigh percentage of forins the structures of which 

 kre markedly difl'erent from those of the species of any other 

 region ; for, in the total of thirty-eight species and varieties 



'which the colleciion contains, fifteen have been found only in 



''Australian seas. 



On this account the main interest of the present Report lies 

 in the additional information which it offers regarding the 

 morphology of species of great rarity, and regarding the varia- 

 tions of structure to which these, and the more widely distributed 

 forms here represented, are subject. The charactfirs of several 

 of the specimens are so distinct from those recorded that I have 



■ found ic necessary to establish for them eight new species Jind 

 • varieties, distributed amongst the genera Lictorella (1 sp.), Cryp- 

 j.tolaria, (1 sp. and 2 vars.), a genus not hitherto known from the 



Australian area, Sertularella (1 sp. and 1 var.), Halicornaria 

 (1 sp.), and Cladocai'inis C?) (1 sp.), also recorded for the first time 



■ from Australia. Of these the most interesting, from a general 

 point of view, is the dimorphic variety of Cryptolaria crassi- 

 caulis, which throws light on the phylogenetic origin of Cry2:>to- 

 laria, and emphasises the close relationship that exists between 

 that genus and Lafo'ea. The gonosome of the widely distributed 

 Lafo'ea serrata has been described for the first time. The com- 

 parative rarity of Gymnoblastic forms and of minute epizoic 

 species is noticeable. 



As to the geographical significance of the collection: — Thirteen 

 species and one variety, each indicated by an asterisk in the 

 following list, have been added to the Hydroid fauna of Austra- 

 lian seas, one of which, Cladocarjnis hathyzonatus, is particularly 

 noteworthy in that it belongs to a well-marked section of the 

 genus Claclocarpus, which has hitherto been regarded as confined 

 to American waters. While it would be presumption to 

 endeavour to deduce with minuteness the wider relationships of 



