264 " ENDEAVOUR " SCIENTIFIC RESULTS. 



and irregular, while in others the sides are quite smooth, 

 though usually a little more elevated than the points where 

 the median teeth would ordinarily be situated ; there is 

 therefore nothing to distinguish the border of such a form 

 from that of a Synihecium. The hydrothecse in question are 

 not immature, but of normal size, and though probably to 

 be regarded simply as a pathological variation, they are 

 none the less significant as indicating the affinities of the 

 species. 



Genus Diphasia, Agassiz. 



DiPHASIA SUBCARINATA (Busk). 



Diphasia suhcarinata, Bale, Biological Results " Endea- 

 vour," ii., 1, 1914, p. 7 (synonymy). 



This species, owing to its possession of an opercular valve 

 consisting of a single adcauline flap, seems to be quite 

 properly placed in the genus Diphasia, notwithstanding that 

 Levinsen makes the absence of teeth on the hydrotheca- 

 margin a characteristic of the genus (while admitting, how- 

 ever, that D. digitalis (Busk) has two feeble lateral teeth). 

 D. suhcarinata has very distinct and well-developed teeth, 

 generally three in number, though in some of the " Endea- 

 vour " specimens one is sometimes obsolete. 



The opercular membranes are very delicate, and many 

 specimens are without a trace of them, but I have some in 

 which they are retained, and it is a very peculiar feature 

 that in many cases there are two distinct opercula, quite 

 similar, but widely separated, one being situated about the 

 middle of the divergent distal half of the hydrotheca, and 

 the other just inside the aperture. The valve itself is simple, 

 and does not extend fully across the hydrothecal cavity, but 

 only about two-thirds of the distance. I have also seen more 

 than two opercula ; this, however, was in hydrothecse in 

 which a regeneration had occurred, and the two normal 

 valves had been retained, while two new ones had been 

 developed. 



Locs. — Great Australian Bight, 40-100 fathoms. 



Off Devonport and Launceston, Tasmania. 



Forty miles west of Kingston, South Australia, 30 fathoms. 



Twent}" miles east of King Island, Bass Strait. 



