330 ROBERTSON 



ALCYONIDIUM POLYOUM Hassall. 



Alcyonidium polyoum Hincks ('8o), pi. LXix, fig. 9. 

 Sarchochitti7n polyotim ]onsSTO's. ('47), pi. lxxi, fig. i. 



Habitat. — On stones, kelp, and on hydroid stems. 



Local distribution. — Orca, Prince William Sound ; Yakutat. 



Foreign distribution. — Dublin Bay; Northumberland; Roscoff. 



The species which I have identified as A. polyou7n forms circular col- 

 onies an inch or more in diameter. In its young state only, can it be 

 described as forming a thin crust. At that stage the boundaries of 

 the zcEcia are distinctly marked off, and it resembles A. mytili very 

 closely. It may be distinguished, however, by the position of the 

 zoecia and by the orifice. The zoecia toward the center tend to be- 

 come upright, and those on the periphery are partially raised, so that 

 the upper portion projects from a gelatinous matrix. They are rounded 

 or barrel-shaped, and the orifice opens upon a distinct papilla. The 

 orifice contains a great number of black sette, some of which project 

 quite far beyond it even when it is closed. The primary crust is quite 

 transparent, but soon thickens into a somewhat fleshy mass of a dark 

 brown color. 



ALCYONIDIUM CERVICORNIS sp. nov. 

 (PI. XXI, figs. 14, 15, 16, 17.) 



Habitat. — On seaweed and on Cellaria borealis. 



Local distribution. — Orca and Juneau. 



Zoarium consisting of a rounded ball-like mass of a dark-brown 

 color. Zoecia imbedded in the gelatinous mass, the orifices projecting 

 above the surface. The surface bristling with tall, red, branching, 

 hollow spines which project from spaces between the zoecia. 



The distinguishing mark of this species consists in the great num- 

 ber of hollow branching spines which beset the surface. Figure 14 

 is a habit sketch, natural size, of a colony. Fig. 15 represents a por- 

 tion of the surface showing a number of the spines and the pro- 

 jecting orifices (or.) of the zoecia. The spines arise from definite 

 portions of the surface, between the zoecia. They are hollow and the 

 interior contains a stainable tissue which extends to the tips of the 

 branches. Each spine consists of a central stem which forks at the 

 top into four branches or prongs. Fig. 16 represents the branches 

 viewed from above. Sometimes the tips of the prongs divide, as rep- 

 resented by fig. 17, and the resemblance to antlers is very marked. 

 In other respects this species bears a resemblance to A. polyorini. 



