630 



YAICHIRÔ OKA DA : 



older zooecia it assumes a bisqui:-:ike shape. The membranous wall 

 of the unusually large compensation sac (fig. a, ce.) passes continu- 

 ously into the zooecial wall at the margin of median pore, besides of 

 course at that of zooecial aperture. So that, the compensation sac 

 opens to the exterior at two places as in Microporella. Operculum 

 (fig. a, op) nearly circular, with weak vertical flange and with sub- 

 marginal sclerite ; occlusor muscles (fig. a, oc.m.) inconspicuous, pro- 

 ceeding from the distal parts of the lateral wall of zooecium and 

 attached to the vertical flange ; divaricator muscle not found. The 

 parieto-diaphragmatic muscle (fig. a, p.v.m.) is strongly developed, 

 springing out from the lateral wall of zooecium and attaching itself to 

 the distal wall of tentacular sheath. There are 17 tentacles. 



A large number of the colonies of this species came under my 

 observation. They were obtained from a considerable depth in the 

 Sagami Sea: viz. Okinosé (195 fms.) ; off Matsuwa (78 fms.) ; off Jôga- 

 shima (depth unknown) ; Yodomi (54-100 fms.) ; Kona in Izu Province 

 (400 fms.). 



2. Adeonella hexangularis, n. sp. 

 Pl. VIII., fig. 10 ; textfig. 7. 



Description of the type : — Zoarium consisting of numerous com- 

 pressed foliaceous branches, rising irregularly from an encrusting base. 

 Branches irregularly divided into lobes of varying size. Young zooecia 

 (textfig. 7 a.) are of a subhexagonal shape, with slightly convex 

 ventral surface surrounded by a single row or double rows of marginal 

 pores ; their aperture is suborbicular with thin and slightly elevated 

 peristome ; median pore numbering from four to eight, always situated 

 below frontal avicularium, minutely fimbriated inside. Old zooecia 

 are of an irregularly hexagonal shape, slightly depressed in front, and 

 exhibit some pores which have decreased both in size and number, 

 due to the progress of growth of the wall. At bifurcating points as 

 well as at indefinite places near lateral edges of most zoarial branches, 



