HVDKOIDA. BALK. 19 



internodes, which are of the double type, are very long, and the 

 two hydrotheca? forming each pair are often widely sepai'ated, 

 so that their paired condition is not obvious. The intei-nodes of 

 the pinnae do not support many pail's only two or three in the 

 specimens examined and many of the distal internodes are 

 single-paired ; but the pairs are far apart and the hydrothecas 

 themselves narrow and but little divergent. The teeth are much 

 shorter than in more typical forms. 



In most varieties the nodes of the stem are well-marked and 

 constricted, but I have seen specimens in which they are faint 

 and not accompanied by any constriction, so that they are 

 scarcely noticeable. 



I have now little doiibt that the Dynamena, attstralis of 

 Kirchenpauer is identical with the smallest variety of this 

 species. I formerly identified with D. anstralis a hydroid which 

 I had previously regarded as a pinnate form of S. Joculosa but 

 which I now believe to be #, in flat a (Versluys), though there is a 

 doubt on the subject until the gonangia are known. Kirchen- 

 pauer' s description, so far as it goes, agrees entirely with my 

 specimens; and though his figure shows the hydrothecse too 

 divergent for average examples it agrees passably with some in 

 my possession. Thompson's account is equally applicable, 

 especially in its reference to the internodes of the pinn 

 supporting either one or two pairs of hydrothecaa ; a feature not 

 noticed by Kirchenpauer. 



Sertularia challengeri, Nutting (Desmoscyphns pectinatiis, 

 Allman), seems also to be no other than the pi-esent species. 

 Allman's figure, which represents the pinna? as divided through- 

 out into single-paired internodes, is not very distinctive, but with 

 the description, may well indicate the small variety. Nutting's 

 description and figure, representing the proximal end of the 

 pinna with more than one pair, is more characteristic, and leaves 

 little doubt as to the identity of the specimen figured.* 



Thai aria heteromorpha, Allman, seems to be distinguished from 

 S. iiiiyuiculata only by the hydrothecae, of which the pi-oximal 

 ones are said to have the margin entire, while the distal ones 

 have the border running out into a single point. I am doubtful 

 whether it is not a form of the present species with abbreviated 

 teeth, approaching the slender variety obtained by the 

 " Endeavour." It has the characteristic stern-internodes of the 

 double type. 



Loc. Bass Strait. 



* Dr. Kirkpatrick, after referring to Allman's type, now confirms this 

 identification. 



