336 M. C. Mereschkowsky on the Hydroida. 
gate oval, narrowed below into a short peduncle, and abruptly 
truncate at the extremity above, where they are narrowed into 
a sort of wide and very short tube. The arrangement of 
the gonophores upon the branches may be in four rows; and 
frequently they are in such great numbers and so close toge- 
ther that they compress one another and then acquire an 
irregular form. When looked at from above they then have 
the appearance shown in the accompanying figure (fig. 10). 
This species, which I only describe very 
briefly now, was at first named by me P. Fig. 10. 
Hincksii; but as I have since convinced 
myself that it was described several years 
ago under the name of Diphasia mirabilis, 
the laws of priority compel me to change 
the name, and to call it Polyserias mira- 
bilis. At the same time I shall change the name of another 
Polyserias, which I have briefly described as P. glacéalis, and 
I shall give it the name of P. Hincksiz, in honour of the Rev. 
Thomas Hincks. The description of this species will follow 
immediately. 
It must be remarked that Polyserias mirabilis is one of the 
most magnificent, and, at the same time, one of the largest 
species that have been met within the White Sea. Nor can I 
say that it is rare, as I have several specimens of it from several 
localities. The largest specimens, which have only retained 
their branches in the upper part, measure nearly 16 centims. 
Their colour is a rather dark brown, darkest especially on the 
principal stem and at the ends of the lateral branches. The 
length of the branches is from 1 to 2 centims., and their width 
about 1:1 millim. Length of hydrothece 0-55 millim., their 
breadth 0°48 ; length of the mature gonothece 1:1 millim., 
their breadth 0-63. 
This species, as indeed the whole genus, is purely polar, 
and apparently even circumpolar. 
Localities.—1. The island of Solowetzky, near the monas- 
tery, at a small depth (not more than 15 fathoms) ; 2. Near 
the promontory of Orlow (White Sea), 67° 17! N. lat. and 
41° 35! EH. long., at a depth of 35 fathoms, on a gravelly 
bottom, June 28, 1876 (gonophores present) ; 8. Glacial Ocean, 
N.E. of the Swiatoy Nos (the Holy Nose), on the Mourman- 
sky bereg, 68° 13’ N. lat. and 40° E. long., at a depth of 60 
fathoms, on a bottom of sand and shells, June 30 (the best 
specimens, with many gonophores). 
