Distribution of certain Hydrozoa. 191 
pean seas will be found to have their relationship based on a 
common arctic origin. 
Mereschkowsky states that he has “found several other 
species of this genus (Polysertas) in the collection of Hydroids 
in the St.-Petersburg Museum of the Academy of Sciences, 
brought from the sea of Ochotsk and Kamtschatka.” It is 
not unlikely that the typical species of Selaginopsis may be 
found in the localities referred to; andthe genus Pericladium 
is also almost sure to live in seas which are midway between 
Alaska and Japan. 
Sertularia fusca, Johnston, of the British seas, is a con- 
necting link between the ordinary species of Sertularta and 
the typical Selaginopsis fusca. 
Selaginopsis fusca of Japan is a connecting link between 
Sertularia fusca, Johnston, and Polysertas Hincksii, Mere- 
schkowsky. 
Each of these might be made the type of a separate genus ; 
but Allman’s genus as characterized will include all; and it 
seems best so to retain it. 
Genus SELAGINOPSIS, Allman. 
“ Trophosome.—Hydrophyton consisting of a single axile 
tube, to which the hydrothece are adnate, and on which they 
are disposed in several longitudinal rows.” 
‘“ Gonosome.—Not known.” [In the British S. fusca, 
Johnston, the gonotheca is pyriform, and borne as in Sertu- 
laria}. 
1. Selaginopsis fusca (Johnston). 
Sertularia fusca, Johnston et auctorum. 
In this species the hydrothecz, instead of being placed on 
the face of the branch as in Sertularia, are inserted on the 
side, the thickness of the branch being much greater in pro- 
portion to its breadth than in that genus. On each of the 
sides the hydrothece are biserial, so far that they are decidedly 
alternate, bending to the right and left, in such a way that 
the mouths of one half only of the cells on each flank are seen 
when one face of the branch is looked at, and the other half 
when the opposite face is examined. It is, in fact, a double 
arrangement of a Sertularella, each lateral view exhibiting a 
series of hydrothecee corresponding to that of the front aspect 
in Sertularella. 
Hab. Distribution as known very limited; confined to east 
coast of the north of England and Scotland. 
