HYDROIDA. BALE. 253 



hydro thecse opposite, just as in the American forms, from 

 which they differed only in their somewhat smaller size. 



In Marktanner-Turneretscher's specimens the hydrothecae 

 do not seem to be opposite or in pairs, although growing on 

 an opposite-celled Synthecium. Warren shows the hydro- 

 thecae in pairs, nearly opposite, on a subalternate-celled 

 Thuiaria. 



From Fraser's account it seems doubtful whether the 

 description of H. calcarata as unbranched is justified. 

 Probably the unbi^anched condition is due to the fact that 

 the specimens examined were usually on hydroid hosts 

 which were themselves unbranched. In H. scandens branch- 

 ing occurs freely. On Sertularella it runs up the rachis, and 

 not only does it send off side branches to the successive 

 pinnse, but on a single pinna it very often divides into two, 

 one running up each side, and in many instances these are 

 united by short transverse ramules. 



While most of my specimens have been found on Sertu- 

 larella divaricata, I have met with single colonies on Diphasia 

 subcarinata, Sertularia macrocarpa, Thyroscyphus fridenfatus, 

 and, as already mentioned, a smaller form on PasytMa 

 quadridentata. Marktanner-Turneretscher found specimens 

 on Synthecium, campylocarpum, and Ritchie on S. orthogonium 

 (the same species ?), and Sertularella adpressa. Borradaile's 

 examples were on Synfheciu7n tubiger {=S. orthogoniura ?) ; 

 Billard's on Thuiaria tubulijormis and Thyroscyphus vitiensis ; 

 Fictet's on Sertularia vegce and S. tubitheca ; and Warren's 

 on Thuiaria tubuliformis. American specimens are most 

 common on Sertularia cornicina and Pasythea quadridentata. 



My specimens of H. scandens have the hydrothecae mostly 

 from .52 to .56 mm. in length, with widths of from .16 to 

 .19 mm. ; the American specimens of H. calcarata average 

 about .59 mm. long and .19 mm. wide, and the small form 

 from Bondi, New South Wales, is only about .44 mm. long 

 and .15 mm. wide. 



Loc. — Forty miles west of Kingston, South Australia, 30 

 fathoms, on Thyroscyphus tridentatus. 



Hebella calcarata (L. Agassiz), 



var. CONTORTA, Marktanner-Turneretscher. 



Hebella contorta, Marktanner-Turneretscher, Ann. K.K. 

 Hofmus. Wien, v., 1890, p. 215, pi. iii., fig. 17a, b. 

 Id., Campenhausen, Abh. Senckenb. naturf. Ges. 



