BY W. M. BALE. 765 



hydrothecse are smooth, or nearly so, and the constriction below 

 the aperture is absent or very slight on the outer side, while it is 

 strongly marked on the inner, so that the terminal portion of the 

 hydrotheca has the aspect of being recurved towards the hydro- 

 can lus, an appearance which is strengthened by the outer marginal 

 tooth being longer than the other two. The hydrothecse in this 

 variety are proportionately longer than in the others. Both series 

 are strongly directed forwards, and when the pinnate form is fully 

 developed the hydrophyton bears a remarkable similarity to that 

 of S. neglecta, from which species it may be distinguished by the 

 pinnae being mostly alternate instead of sub-alternate, and being 

 given off below each hydrotheca on the pinnate part of the stem 

 instead of below every second one on each side, by the much 

 shorter marginal teeth ot the hydrotheca, and by the internal 

 teeth, also by the different gonangia. 



While it must be admitted that the arrangement of these 

 varieties under one species is not perfectly satisfactory, they appear 

 to run into each other by so many intermediate forms that I have 

 so far failed to find any distinct line of demarcation between 

 them. It is not improbable that S. indivisa will have to be 

 referred to the same species, and perhaps S. solidula. All the 

 varieties possess teeth within the hydrotheca-margin, one within 

 each of the two upper sides, and either one or three within the 

 lower side. The hydrotheca often has two minute rod-like 

 thickenings of the perisarc about midway down, on opposite sides. 



SERTULARELLA SOLIDULA, Bale. 



(Plate XV., figs. 3-4). 



A specimen from Bondi, with the ends of the hydrothecse curved 

 outwards rather more than those of the type form. 



SERTULARELLA CYLINDRICA, n.sp. 



(Plate XVI., fig. 7). 



Hydrocaulus about half an inch in height, simple or slightly 

 branched, divided by oblique joints into internodes of moderate 



