HYDKOIDA. BALE. 321 



tasmanica, though less regular. The very short closely- 

 ranked hydrocladia are very distinctive, no less than the 

 peculiar form of the hydrothecae and the median sarcothecse, 

 some of the descriptions of which have been by no means 

 correct. This, as Allman pointed out, is the case with Kirchen- 

 pauer's statement that the mesial sarcotheca exceeded in 

 width the hydrotheca itself. Allman's account of the 

 hydrotheca-margin as being quite smooth is also erroneous, 

 according to Billard, who has examined the original " Chal- 

 lenger " specimens. The oblique line which crosses the 

 hydrotheca near the base, is the ordinary intrathecal fold 

 found in a similar position in most species of Aglaophenia, 

 but the longitudinal line is not, I think, found elsewhere. It 

 runs from the top of the lateral sarcotheca to the base of the 

 hydrotheca, and in a strict profile view it keeps parallel with 

 the abcauline side of the hydrotheca, crossing the intrathecal 

 fold. It is an extremely fine line, so delicate that it may 

 easily be overlooked, except at its origin above the lateral 

 sarcotheca, where it is slightly thicker ; and in many of the 

 hydrothecse I failed to distinguish it. 



There are commonly only two septal ridges in the internode, 

 though in a few cases I have seen a third, which was almost 

 coincident with the proximal node. In one of the rough 

 sketches made by Mr. Busk an internode is seen with appar- 

 ently four ridges ; this results from the specimen being seen 

 obliquely, so that the ridges on both sides of the internode are 

 visible at once. The dorsal ridge, which unites the two trans- 

 verse ones, is a very distinct feature in a back view of the 

 hydrocladium when strongly marked ; in some specimens, 

 however, it is weak and obscure. 



The lateral sarcothecse are much like those of A. billardi, 

 etc., except that they are considerably stouter in proportion 

 to their length. The septum dividing the mesial sarcotheca 

 has in side view, as Billard remarks, a sigmoid form ; it has 

 a narrow opening on the side next the hydrotheca. The 

 terminal aperture, with its lateral lobes, is evidently formed,, 

 as in many other species, by two apertures cutting into each 

 other. 



The gonangial structures are really less exceptional in 

 character than the trophosome, the series of large dish-shaped 

 receptacles along the upper side of the corbula, shown in the 

 " Challenger " Report, having no real existence. There are 

 none of the large expanded free portions of the corbula-leaves, 

 such as are found in most of the species described in these 

 Reports ; the distal edges, with their closely-ranged sarco- 

 thecae, only projecting slightly outwards. The series of 



