HYDROIDA. BAIiB. 



23 



The stem-iuternodes usually bear three hydrotheca? ; those of the 

 pinna? mostly support only one, though the larger pinna?, which 

 themselves bear secondary pinna?, tend towards the same 

 structure as the stem. The internodes vary much in length, the 

 distal ones which I measured averaged about '49 mm., but on 

 the older part some of them reached about 75 (in all cases the 

 measurements are of internodes with a single hydrotheca only). 

 The hydrotheca? themselves measured from the base to the top of 

 the lateral teeth about '40, and their diameter at the base of the 

 free portion about 2 1 . They are aduate about two- thirds of their 

 height, and mostly directed slightly forward, though in other 

 parts of the same colony they may be in the same plane. They 

 are moderately divergent laterally, and occasionally the outward 

 bend is rather abrupt. The free part is tubular, not distinctly 

 conical. The gonangia average about P40 to T50 in length by 

 •89 in width ; the annulations, of which there are about nine, are 

 very prominent ; the aperture has an internal diameter of about 

 T6 to -18, with an everted lip about T9 to '22 across, and having 

 an irregular ragged edge, as shown by Hartlaub. 



2. Great Australian Bight, 1911.— The habit is similar to the 

 last, but the hydrotheca? are a fraction larger ('41 by '22), with 

 the free part very slightly conical ; they are more frequently in a 

 single plane, but many are distinctly directed forward. Some of 

 the single internodes reached about 90 ; the distal ones are of 

 the same length as those of No. 1. The gonangia are wanting. 



3. Var. dubia, Bale, Bondi Bay. — The ramification is pinnate, 

 but irregularities are frequent. The internodes are short, the 

 distal ones only about -30 and the proximal "38. The hydrotheca? 

 average "37 by "18, and may be in one plane or somewhat 

 directed forward. The gonangia measure about 1*18 by '67, and 

 differ considerably from all the other varieties, being of greater 

 diameter from back to front and having the top sloping very 

 much downward, so that the summit rises at the back well above 

 the level of the aperture, which is far forward. The annulations 

 number eleven or even twelve, and are more regular and closer 

 than in the other varieties. The aperture is very wide, about *18 

 to *19, and the basin-shaped lip has a diameter of about '28, 



4. Port Phillip, 1890. — The ramification is fairly regular, the 

 internodes strongly marked and somewhat longer than those of 

 var. dubia, the hydrotheca? the smallest of any of the varieties 

 (•31 by "15), and in their more conical form as well as their size 

 they come nearest to S. johnstoni. The gonangia, however, are 

 not at all like those of that species. They are about 

 1"33 by 74, with eight or nine strong annulations ; the 

 aperture is about * 13 to '15, and the basin-shaped lip reaches *24 

 to '30. 



