173 HYDROIDA. BALK. 



Sarcotkecte bitbalamic, canaliculate; one, scoop-shaped, stout 

 aud rigid, in front of the hydrotheca, to which it is almost 

 appressed ; two, large, wine-glass-shaped, at the sides, on rather 

 high peduncles ; two, very small, under the back of the 

 hydrotheca and two larger ones just above, one or two on the 

 proximal internode of each hydrocladium, and generally a double 

 series running down the proximal part of each brauchlet (below 

 the double joints) ; only the laterals freely moveable. 



Gonotheca? large, urceolate, slightly narrowed upward and 

 again expanding to the summit, margin circular, oblique, not 

 contracted nor thickened ; a stout transverse ridge inside the 

 front a little below the margin ; a large operculum the full 

 width of the gonotheca, slightly convex in the middle, situated 

 inside the margin and resting on the internal ridge in front ; 

 several large sarcotheca? (often five or six) surrounding the base. 



Colour. Blackish in some colonies, very pale-brownish in 

 others. 



This remarkable species, which was first made known by me 

 under the name of P. agla&gihenoides, has been identified by 

 Billard with P. sulcata, one of the species named, but not 

 adequately described, by Lamarck. My original specimen was a 

 fragment only, but the species has been further described by 

 Billard, and also by Ritchie, who obtained specimens from the 

 " Thetis " collection. Some finer specimens than have hitherto 

 been observed are among the material dredged by the 

 " Endeavour," and some of them include the gonangia, not 

 heretofore described. 



The largest specimen is about eighteen inches high and three 

 to five wide, with eight or nine main branches and many smaller 

 ones. The stem is over one-third of an inch in diameter at the 

 base, and is bare only for the lowest two or three inches. The 

 stem and branches are regularly flexuons, the pinnately-disposed 

 branchlets* springing from the flexures alternately on each side. 



The ramification is different from that of any other species 

 which I have examined, and I have not succeeded in tracing 

 clearly the origin of the branchlets. They are not given off, as 

 in most species, laterally from a distinct primary stem, but their 

 proximal portion is continued without interruption into the 

 fascicle of tubes which make lip the stem or branch, and may 

 be traced for some distance down till they are lost to sight among 



*I prefer the term "branchlets" to "primary hydrocladia" for con- 

 venience, and also because in bearing hydrothecae as well as hydrocladia 

 they merely agree with the branches :md stems of many species of 

 Plumularia, which nevertheless conld not with propriety be classed as 

 " hydrocladia." 



