HYDROIDA. — BALE. 317 



Trifling differences in the habit of this species and A. 

 tasmanica., referred to in the original descriptions, do not 

 prove sufficiently constant to be of much value in determining 

 the species. The most reliable distinction, so far as the 

 trophosome is concerned, is in the longer and narrower hydro- 

 thecae of A. hiUardi. It is now known that the male corbulse 

 differ in the two species (see A. tasmanica). 



iyOC5.— Great Australian Bight, 40-100 fathoms, 130-190^ 

 fathoms, and 80-120 fathoms. 



Great Australian Bight, Long. 130° 40' E., 160 fathoms. 



Aglaophenia tasmanica, Bale. 



Aglaophenia tasmanica., Bale, Biological Results " Endea- 

 vour," ii., 1, 1914, p. 37, pi. iii., fig. 2, pi. vi., fig. 2. 

 Id., Briggs, Rec. Austr. Mus., x., 10, 1914, p. 300, pi. 

 xxvi ; Id., Briggs, Proc. Roy. Soc. N.S. Wales, xlviii., 

 1915, p. 316. 



In some of the specimens a good deal of variation exists in 

 regard to the length tf the mesial sarcothecse, which are 

 sometimes not longer, proportionately to the hydrothecse, 

 than those of A. billardi. In specimens collected near Cape 

 Pillar, Tasmania, Mr. Briggs has found the male corbulae, of 

 which he has obligingly forwarded me examples. Considering 

 that A. tasmanica and A. billardi are such extremely close 

 allies, and that their female corbulse do not differ in any 

 important particular, it would naturally be expected that a 

 corresponding likeness would be found between the male 

 corbulse ; such, however, is not the case. Those of A. 

 billardi are cylindrical, closed throughout, and of equal 

 diameter from end to end, while in A. tasmanica they are, as 

 Mr. Briggs has pointed out, narrowed towards the end in 

 consequence of the leaflets becoming gradually shortened,, 

 and also separate, just as in yl. dannevigi and A. macrocarpa. 



In the female corbulse the lateral spurs, which spring out- 

 ward and forward from the distal edges of the corbula-leaves 

 attain a large size, and in some cases I have noticed that 

 their distal portions, which are incurved towards the rachis, 

 coming into contact with the proximal parts of the next 

 spurs, attach themselves to them, so as to form a series of 

 joined arches along each side of the gonocladium. 



The male corbulse have the last four or five leaflets on each 

 side separate, broadly truncated, and progressively shorter 

 and shorter, till the final pair are reduced close down to the 

 lateral spurs, which are not shortened, but extend forward 

 beyond the termination of the corbula-rachis. 



