314 " ENDEAVOUR " SCIENTIFIC RESULTS. 



Billard formerly suggested the identity of A. acanthocarpa 

 with A. divaricata, and the present variety seems to bridge 

 the difference which appeared to exist between them. I do 

 not, however, concur in the reference of A. laxa, Allman, to 

 the same species, nor do I think that Thecocarpus laxus of 

 Billard's " Siboga " Report is the same as A. laxa. Hilgen- 

 dorf 1 has described the corbula of a species which he considers 

 to be ^. laxa, and specimens of this species, which Mr. Briggs 

 has kindly sent to me, come decidedly nearer to Allman's 

 account than does Thecocarpus laxus. The corbula is of the 

 same type exactly as that of ^4. divaricata and ^. acanthocarpa, 

 and bears no hydrothecae. Where the specimens differ from 

 Allman's account is in the septal ridges of the hydrothecal 

 internodes, the one which Allman says is opposite the base of 

 the hydrotheca being absent, while the front one is oblique ; 

 in short the condition is just as figured for A. acanthocarpa. 

 In both A. laxa and A. acanthocarpa, as in A. divaricata, the 

 intrathecal ridge, with its corresponding septal ridge, is set at 

 or near the middle of the internode, instead of near the base 

 of the hydrotheca, as in T. laxus and most other species. In 

 T. laxus the third tooth on each side of the hydrotheca is 

 widely everted, which is contrary to the condition in A. laxa. 

 The latter has smaller and narrower hydro thecae than A. 

 acanthocarpa, and the front is somewhat incurved between 

 the anterior tooth and the mesial sarcotheca, which does not 

 extend to the aperture. In var. acanthocarpa, as in other 

 forms of A. divaricata, the hydropore extends quite from side 

 to side of the hydrotheca, so that in a lateral view the proximal 

 half of its cavity appears completely continuous with that of 

 the internode ; this is not so noticeable in A. laxa, though 

 here also the hydropore is very large, which accounts for the 

 forward position of the intrathecal ridge. The latter is a mere 

 fold in the hydrotheca-wall, the shelf-like portion on the 

 adcauline side being even more rudimentary than in any of 

 the varieties of A. divaricata. The anterior tooth of the 

 hydrotheca has frequently an erect crest. 



I have met with var. acanthocarpa (?) onlj^ in material 

 from Port Jackson, New South Wales. 



AgI;Aophenia divaricata {Busk), 



var. CYSTIFERA, var. nov. 



Distinguished from the type by the great enlargement of 

 the upper of the two cauline sarcotheca? which are borne by 

 the hydrocladiate internodes of the rachis. 



1. Hilgeiuloif— Trans. N.Z. Instit., xliii., 1911, p. 541, figs. 1-3. 



