Vor. 2] Robertson.—Non-Incrusting Bryozoa. 241 
Spine—a jointed or unjointed process found on the margin of the 
aperture (fig. 1 of the text, sp.). 
Tentacle-sheath—the delicate membrane of the introvert which incloses 
the tentacles when the polypide is retracted. (Text fig. 1, tent sh.) 
Vibraculum—a chitinous seta of varying length, depending on the 
species, extending from a chamber on the dorsal side of the 
zocecium (PI. IX, figs. 41, 45, v.). 
S 
Vibracular chamber—a chamber on the dorsal side of the zocwcium in 
some of the Cellulariide, resembling an avicularium, from which 
extend a hairlike process called the vibraculum, and the rootlet 
(Pl. IX, figs. 42, 46, v. ch. and v.). 
For purposes of orientation, it must be explained that the 
front or ventral side of a zocecium is that on which the aperture 
with its operculum occurs; the side opposite is the dorsal. The 
top of a zocecium, and the ends of the growing tips of branches 
or colony are referred to as the distal or anterior end of zocecium, 
or extremity of branch or colony; the lower part or end nearest 
the root or point of origin, as the proximal or posterior extremity. 
Thirty-four species and one subspecies belonging to thirteen 
genera are here recognized. Of the genera, Stirparia has as 
yet been reported only from Australia; Synnotum only from the 
Adriatic; and Corynoporella only from Greenland. Of the 
whole list, thirteen species and one subspecies are new, while 
twenty species and one subspecies are restricted to the Pacific 
Coast.. The ovicells of Aetea anguina are here described and 
figured for the first time, as are the avicularia and ovicells of 
Stirparia, and the ovicells of Corynoporella. 
LIST OF SPECIES TREATED. 
Aetea anguina Linneus. Bugula pacifica Robertson. 
Aetea truncata Landsborough. Bugula flabellata Thompson. 
Eucratea chelata Linneus. Bugula pugeti sp. nov. 
Gemellaria loricata Linnveus. Bugula curvirostrata sp. nov. 
Menipea ternata Ellis and Solander. Bugula longirostrata sp. nov. 
Menipea gracilis Busk. Bugula laxa sp. nov. 
Menipea occidentalis Trask. Beania mirabilis Johnston. 
Menipea occidentalis catilinensis Beania longispinosa sp. nov. 
subsp. nov. Stirparia ciliata sp. nov. 
Menipea erecta Robertson. Stirparia occidentalis sp. nov. 
Menipea pribilofi sp. nov. Stirparia californica sp. nov. 
Scrupocellaria californica Trask. Corynoporella spinosa sp. nov. 
Scrupocellaria varians Hinecks. Synnotum aviculare Pieper. 
Scrupocellaria diegensis sp. nov. Cellaria borealis Busk. 
Caberea ellisi Fleming. Cellaria mandibulata Hincks., 
Bugula neritina Linneus. Cellaria diffusa sp. nov. 
Bugula murrayana Johnston. Tlustra lichenoides Robertson. 
Bugula californica sp. nov. Flustra membranacea-truncata Smitt. 
