fi'om the North Pacific Ocean. 435 



1. Selaginopsis trtseriah's, sp. n. (PL XVI. iigs. 1, 2.) 



Trophosome. Hydrocaulus straight, not angularly bent, 

 broader than the branches. Branches arranged alternately 

 and subspirally, springing from all sides, diminishing towards 

 the apex, and ramifying several times. The hydrotheca?, 

 almost entirely immersed in the axial tube and of a cylin- 

 drical form, a little narrowed towards the orifice (which is 

 oval with two angles), are placed in three longitudinal series. 



Gonosome. Not known. 



Locality. Kamtschatka {M. Kastelshy). 



This small species, which comes from Kamtschatka, is 

 represented in the Academy's collection by only a single 

 specimen (PI. XVI. fig. 1), 37 millims. long. The lower 

 extremity of the stem, with a small disciform enlargement, 

 was not fixed to any object. The general form of the colony 

 is conical ; it diminishes very gradually, so that at its apex 

 it is more or less pointed. The stem is straight, divided into 

 internodes, each having from two to four branches, and bears 

 annulations at its base. The branches, which are arranged 

 on all sides of the principal stem, are excessively slender 

 compared with those of all the other species of this genus, 

 which is explained by the small number of series (three) in 

 which the hydrotheca3 are arranged ; they are placed at an 

 acute angle to the princij)al stem, and become shorter and 

 shorter as they approach the apex ; they may divide in their 

 turn, usually two or three times, rarely more. The hydro- 

 thee* are arranged in three regular series (PI. XVI. fig. 2), and 

 in such a manner that no two orifices of the three series come 

 at the same level ; this character of the arrangement of the 

 hydrothecte in three series is perfectly constant in the species 

 in question. The hydrothecas are almost entirely immersed 

 in tlie axial tube, to which they are adnate ; their orifices, 

 which are compressed, oval, and furnished with two angles, 

 alone project more or less, but in all cases very slightly, from 

 the surface. The two angles are always distinct, although 

 they are not produced into two distinct teeth as, for example, 

 in Selaginopsis mirahilis. The form of the hydrothecee is 

 more or less cylindrical, narrowing a little towards the upper 

 extremity. A small tube with its margins slightly reverted 

 establishes the communication between the cavity of the 

 hydrotheca and that of the axial tube, in the same m.anner 

 as is described by me in Selaginopsis HincJcsiiy mihi. 



Width of a branch 0*55 millim. } length of a hydrotheca, 

 0*45, its maximum breadth 0*25, 



29* 



