HYDROIDA. BALE. 313 



In other respects than those enumerated above the variety 

 agrees with A. divaricata. It is a dwarf form, the largest 

 specimen which I have met with measuring one and a half 

 inches, but it is usually only about half that height. These 

 small forms have generally not more than one accessory 

 tube in the stem. The most characteristic feature is the 

 form of the mesial sarcotheca, which follows the curve of the 

 hydrotheca nearly to the margin and then curves upwards. 

 The intrathecal ridge is a distinct partition extending half 

 through the hydrotheca in an oblique direction, parallel with 

 the border. 



I can find no difference whatever in the corbulae. 



This variety does not occur among the " Endeavour " 

 specimens. 



AGLAOPHENIA DIVARICATA (Busk), 

 var. ACANTHOCARPA, Allman ? 



? Aglaophenia acanthocarpa, Allman, Journ. Linn. Soc., 

 Zool., xii., 1876, p. 274, pi. xxi, figs. 1-4. 



Aglaophenia divaricata, var., Bale, Cat. Austr. Hydr. Zooph., 

 1884, p. 164. 



Distinguished from the type by the presence of an oblique 

 septal ridge in the internode, starting from the base of the 

 lateral sarcothecse, and by the smaller and more sharply 

 triangular teeth of the hydrotheca-border. 



The life-size figure given by Allman of A . acanthocarpa does 

 not agree well with any specimen of this group which I have 

 observed, still it recalls Busk's description of A. ramosa, 

 which he says has the branches ''' rising in great numbers 

 almost immediately from the mass of radical fibres." In 

 other respects my specimen (from Port Jackson, New South 

 Wales), agrees very fairly with Allman's account. As 

 already mentioned, many specimens of A. divaricata occur in 

 which the bases of the lateral sarcothecse do not, as in typical 

 forms, coincide with the base of the intrathecal ridge ; the 

 same condition prevails in the present form, but there is a 

 strong septal ridge, in addition to the median one which alone 

 exists in the type. The intrathecal ridge is an extremely 

 narrow shelf, and gives origin to a fold in the hydrotheca-wall, 

 very much as in the type. 



In these specimens the lateral sarcotheca3 towards the ends 

 of the hydrocladia are not nearly so much enlarged as is 

 usually the case with the typical A. divaricata. 



