HYDROIDA. BALE. 21 



Hydrotheca 1 tubular or sub-conical, both series in one plane, 

 or directed more or less forward, and varying considerably in the 

 extent to which they are divergent laterally, often with a 

 somewhat abrupt bend outward ; margin with three teeth, one 

 superior and two lateral, and an operculum of three pieces; no 

 internal teeth. An apparent oblique septum crossing the interior 

 of many of the hydrotheca?. 



Gouothecae large, borne on the pinna?, surrounded by a 

 number of prominent annular ridges except on the back, which 

 is smooth and appressed to the pinna; the extreme distal 

 portion of the gonotheca projecting forward and having the 

 ridges completely annular ; aperture exceutric, very variable in 

 width, with the lip more or less everted or funnel-shaped. 



Under S. divaricata I include the species originally described 

 by me under that name, with vars. dtibia and subdicliotoiua (the 

 latter being synonymous with ,S'. siibdtchotoma, K.) and the 

 variety which I formerly described as the Bass Strait form of 

 8. johnstoni, but which, in accordance with Hartlaub's classifi- 

 cation, must be considered distinct from that species ; together 

 with such varieties as are so closely allied to the foregoing as to 

 preclude, in my opinion their specific separation. The species, 

 so constituted, is extremely variable, in fact out of nine 

 preparations which I possess from various localities no two are 

 completely alike. 



The points of difference are the ramification, the presence or 

 absence of a distinct joint between every two hydrothecaa, the 

 length of the internodes and consequent distance apart of the 

 hydrotheca?, their position in one or two planes, their lateral 

 divergence and whether such divergence is abrupt or gradual, 

 and the extent to which they are adnate ; and, as regards the 

 gouangia, their size and form, the number and prominence of 

 their annulations, and especially the size and form of the mouth. 

 The presence of an apparent septum in the hydrotheca, and the 

 tendency of many of the ramules to run out into twisted tendrils, 

 which may become attached to other portions of the polypidom, 

 are characters which, I believe, are found more or less frequently 

 in all the varieties. 



The essential character of S. sitbdichotoin., as described by 

 Kirchenpauer, was the irregular ramification as opposed to the 

 pinnate habit of tf. divaricata. The gonangia were not in 

 question, as neither Busk nor Kircheupauer were acquainted 

 with the gouangia of S. divartcntft, and it may be pointed out 

 that it is quite as likely as not that Busk's original species may 

 have had gonangia similar to those of the var. subdirlinfnma, 

 Hartlaub, finding that the ramification was too inconstant to 



