HYDROIDA. BALE. 41 



The hydrotheca of A. crucialis, according to Billard, most 

 resembles that of A. macrocarpa, but Eitcliie describes the 

 lateral lobes as obsolete in many of his specimens. I do not find 

 much variation in this particular in any of the forms described 

 above, if care is taken that the hydrofhecas are viewed in exact 

 profile, though A. tasmanica and A. billardi may exhibit 

 such lobes when lying obliquely. The mesial sarcotheca, 

 in Di\ Hillard's sketch, resembles that of A. tasmanica, except 

 that the aperture is more oblique. 



Reference to the descriptions of the corbula? of A. tasmanica 

 and A. billardi will show that there is no difference except such 

 as is due to the somewhat more luxuriant growth of the former, 

 as evidenced in the fuller development of the lateral spurs, and 

 also of the superior crests. In A. macrocarpa the male' 

 corbula) only have been observed, and these in but a single 

 specimen ; their leaflets do not meet continuously, but on the 

 upper part of the corbula they become separate at intervals, 

 both edges being fringed with sarcothecge at those pai-ts. 



So far as A. tasmanica, A. billardi, and A. macrocarpa 

 are concerned the foregoing descriptions will I think suffice 

 for their discrimination, but A. crucialis, as described by 

 Mr. Ritchie, seems to combine some of the characters which 

 differentiate these forms, e.g., the size of the hydrotheca?, the 

 form of the hydrotheca-margiu, and the structure of the corbula. 

 It is not stated whether the differences referred to are found in 

 the same colonies ; if so an extent of variability would be 

 indicated which might require that A. tasmanica at least should 

 be recognized as within the range of variation of A. crucialis ■ 

 otherwise it is possible that more than one type is represented in 

 the specimens. But undoubtedly the three forms which I have 

 described are amply distinguished from one another, so far as 

 present information shows, whatever may be their relations with 

 Lamouroux' species, not yet completely elucidated. 



Ac.LAOPHENIA DANNEVtGI, S[i. )WV. 



(Plate iii., fig. 4 ; Plate vi., fig. 4.) 



Hydrophyton polysiphonic, two feet or more in height, stems 

 thick, densely and profusely branched from near the base to the 

 summit ; young branches mostly in opposite pairs, their anterior 

 aspect facing that of the parent branch, ascending at an angle of 

 about 20 g laterally, and projecting forward at about the same 

 angle ; each branch springing from an internode of the primary 



