768 SOME NEW AND RARE IIYDROIDA IN THE AUSTRALIAN MUSEUM, 



at the same time the free portion is not nearly so divergent as is 

 generally the case with S. orthogonia. The aperture is at right 

 angles to the teraiinal part of the hydrotheca, and the margin is 

 slightly sinuated at the two sides, while it is more everted than in 

 >S. ortJwgonia, and lines of growth seem rare. It is true that ia 

 each species calycles may be found which are somewhat inter- 

 mediate, but there is no difficulty in distinguishing between such 

 specimens as I have met wich ; I therefore hesitate to unite them 

 without further evidence. 



The gonothecse are large and compressed, so that in an ordinary 

 view of the polypary they are seen edgewise, the transverse 

 undulations then appearing very distinct. These undulations, 

 however, do not run round the gonotheca, but are confined to the 

 two broader sides, and gradually smoothed away towards the 

 narrower sides, so that if the gonotheca be viewed in its broader 

 aspect its outline appears smooth or nearly so. In Professor 

 Allman's two species the undulations are continued till they meet 

 two zig-zag median lines which run down opposite sides of the 

 gonotheca ; the gonotheca^ also are much shorter than those of 

 S. ortJiogonia, and apparently not so compressed. One fragment 

 of S. ortlioyonia, found among the rest, has gonothecse not unlike 

 those of Allman's species in size and .shajje, and showing 

 chitinous ridges in the front view, which however do not run 

 straight across to meet a mesial line, but form an entirely irregular 

 network. I am not aware of the signification of these peculiar 

 gonangia, so different fiom the ordinary ones, but they may be due 

 to an accidental deformity. 



The hydrotheci3e of »S. orthogonia are usually directed outwards, 

 but in some specimens they are also turned towards the front, the 

 opposite hydrotheca; being almost in contact in the front of the 

 polypidom. 



Sertularia geniculata, n sp. 



(Plate XVII., figs. 6-11). 



Hydrocaulus .simple, minute, with a pair of hydrothecae on each 

 internode, joints slender. Hydrothecae opjiosite, in contact with 



