from the North Pacific Ocean. 437 



fig. 3). The colony is regularly pinnate ; the branches, 

 springing at an acute angle, are arranged alternately ; they 

 are of moderate length, and only diminish towards the extre- 

 mity. Usually each internode bears three pairs of branches. 

 The branches are cylindrical, straight, with their surface 

 smooth (which distinguishes them from those of Selaginopsis 

 mirahiUs)^ uniting with the hydrocaulus by a short constric- 

 tion ; their colour is of a very light brown, never becoming 

 darker towards the end, as is always the case in 8. mirabilis. 

 Sometimes, although very rarely, a branch gives origin to 

 a secondary branch let near its extremity. 



The hydrothecjB are arranged in two series upon the prin- 

 cipal stem, and in four regular longitudinal series upon the 

 branches ; and this character is perfectly constant (PI. XV I. 

 fig. 4). Their form is not very characteristic; the hinder 

 part, which is the widest, is rounded, and communicates with 

 the tubular axis by a small tube with the margins slightly 

 reverted. A little neck in the form of a very short tube is 

 placed vertically to the surface of the stem and turned out- 

 wards ; it terminates in an ajierture, which is large, oval, and 

 usually furnished with two angles, which, however, are 

 scarcely, if at all, produced into teeth, as also in Selaginopsis 

 triserialis ; but here it sometimes happens that there is no 

 angle and the orifice appears regularly oval or even round. 



Length of the largest individual 180 millims. (it is there- 

 fore one of the largest species) ; breadth of the colony about 

 from 30 to 35 ; length of the branches usually 20, sometimes 

 25 ; breadth of the hydrothccse 0'27, of all the branches 0'5 j 

 length of the hydrothecaj 0*5 ; diameter of the aperture 

 0-14. 



This fine species is represented in the collection of the 

 Museum by several large specimens attached to fragments of 

 Modiola modiolus ; it most nearly approaches Selaginopsis 

 Hincksiij mihi, by its mode of ramification, the fact that the 

 surface of the branches is smooth, and the form of its hydro- 

 thecse. But it differs therefrom essentially by its four series 

 of hydrothec^ {S. Hinchsii always has six), as also by the 

 smaller length and breadth of its branches. At present I 

 know five species of this genus which have colonies of a 

 plumose form — namely, S. mirabilis , Verr., S. Hinchsvi^ 

 mihi, S. Allmani, Norm., S.fusca, Johnst., and S. pinnata^ 

 mihi; all the other species have branches springing not from 

 two sides only of the principal stem, but from all sides, thus 

 aflfecting a habit quite different from that of the above five 

 species. 



