164 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 14 



the distal wall is similar to Bugula. The ooecium is more like that of 

 Dendrobeania and the close association of the zooecia in a broad layer 

 resembles that of D. (Bugula) laxa (Robertson) and especially D. 

 (Flustra) lichenoides (Robertson), both of which are repent. The en- 

 crusting zoarium, the very extensive gymnocyst which bears pedunculate 

 avicularia and spines, and the absence of radicles appear to exclude it from 

 any known genus. 



Sessibugula translucens new species 

 Plate 26, figs. 1, 2 and 3 



Zoarium loosely encrusting on smooth surfaces, forming flat colonies. 

 Zooecia large but quite variable in size, 0.65 to 0.95 mm long by 0.30 

 to 0.45 mm wide, closely associated without any evidence of fenestrae, 

 forming a smooth, thin and often almost transparent crust. The opesia 

 is irregularly ovate or elliptical with a raised margin, occupying about 

 the distal half of the front. The walls are very thin, the lateral walls 

 scarcely separable. The gymnocyst is extensive, occupying the proximal 

 half of the front and is quite transparent; bearing spines and stalked 

 avicularia. The cryptocyst is barely traceable as a minutely beaded border. 



Spines : a tall tubular spine on each side toward the distal end, bend- 

 ing slightly across the opesia ; 1 or 2 erect spines on the sides, often want- 

 ing; a pair of similar spines on the distal border of the gymnocyst, some- 

 times only one median spine, occasionally 4 or 6, curving forward over 

 the opesia. 



Avicularia buguloid, moveable on a short peduncle, characteristically 

 paired and well separated one on either side of the midline, only one 

 may be present, either lateral or median, or occasionally both wanting; 

 length 0.18 to 0.26 mm; rostrum decurved at the tip, the mandible 

 evenly arcuate, with a small curved tip. 



Ovicell hyperstomial, evenly rounded, attached to the distal end of 

 its zooecium by a rather broad base; the surface faintly and radiately 

 striate; width 0.22 mm, length 0.20 mm. 



The frontal membrane is delicate and there is no evidence of a chitin- 

 ized operculum. There are multiporous septulae in the lateral walls and 

 a row of uniporous septulae in the distal wall. Radicles wanting. 



Type,AHFno.41. 



Type locality, Hancock Station 557-36, ofiE White Rock, Isla Partida, 

 Gulf of California, 28°55'30''N, 113°05'35''W, 45 fms, four colonies; 

 also at 468-35, Port Parker, Costa Rica, 5 fms, one colony; 147-34 and 

 155-34, Tagus Cove, Albemarle Island, Galapagos, 30 to 60 fms. 



