BY W. M. BALE. 775 



of which, situated in the axil, is larger than the other, and both 

 are simply conical projections. In a specimen from Queenscliff 

 the axillary sarcothecse have a distinct incomplete partition just 

 within the aperture, but this bithalamic condition is absent from 

 the others. In several specimens I could only distinguish the axial 

 sarcothecte. Besides the sarcothecse already mentioned there is 

 sometimes one at the summit of each stem-internode in front. 



The mesial anterior sarcothecse consist, in their perfect form, of 

 a lower chamber, or protuberance of the pinna, terminating in a 

 shallow concave or saucer-shaped receptacle facing the hydrotheca, 

 and emarginate below, where the rim terminates at each side by 

 becoming united to the pinna. In Mr. Whitelegge's specimens 

 however, the wall of the upper loculus is usually cut away on both 

 sides so that there remains only a scoop-shaped projection directed 

 towards the hydrotheca from the top of the lower chamber, and 

 presenting, when seen in front view, a more or less rectangular 

 form. Some of the sarcothecae however approximate to the 

 ordinary form, while different varieties of the species present 

 various intermediate forms between the extremes above-mentioned. 



There is a striking resemblance between this species and the 

 DiplocJwilus mirabilis of Professor Allman's " Challenger " 

 Report, so far as the more important structural features are 

 concerned. Both species agree in the absence of the supraca- 

 lycine nematophores, and in having the anterior nematophore 

 unattached to the calycle, and even the peculiar form of the 

 nematophores appears almost alike in both species, except that 

 those of A. productum are more erect. The only distinction 

 of more than specific value is the presence in D. mirabilis of an 

 external envelope surrounding the upper part of the hydrotheca, 

 and from analogy with several other species it seems extremely 

 probable that the external envelope is really the outer surface of 

 a thickening of the calycle, and not a distinct structure. Such 

 thickenings of the perisarc are by no means rare, familiar examples 

 being the stem-internodes of Obelia yeniculata and the calycle- 

 wall of Campanularia caliculata, while in Eucopella we have an 

 extreme case, the hydrotheca being almost entirely filled by a 



