ANTARCTIC BRYOZOA — ROGICK 257 



width on three readings. The internal avicularial mandible is of 

 similar shape and appearance as mandibles of external avicularia 

 (pi. 12,F). 



The external avicularium is placed transversely beneath the orifice 

 and to one side of the midline with the hemispherical (back) area 

 in or touching the midline (pi. 12,C,D,G). A mucro tips its beak 

 forward (pi. 12,D). Another mucro grows at its base, on the opposite 

 side of the midline (pi. 12,B,D). The avicularial beak makes an 

 approximate 110° angle with the semicircular area back of the man- 

 dible (pi. 12, G). External avicularium measurements: total length 

 0.216-0.288 mm. (average 0.264 mm.); total width 0.158-0.187 mm. 

 (average 0.174 mm.); beak length 0.130-0.187 mm. (average 0.160 

 mm.); mandible length 0.101-0.122 mm, (average 0.133 mm.); 

 mandible width 0.115-0.144 mm. (average 0.133 mm.). 



All zoids had external avicularia. 



Frontal oral ledge: A gently curved ledge (pi. 12,C-E, and fl 

 of pi. 12,1) shields the internal avicularium from the outside. It is 

 placed diagonally at a slight angle to the frontal surface (pi. 12,C, 

 and fl of pi. 12,D). The angle is much smaller in this species than in 

 C. roydsi. Compare the orifices and oral ledges of plate 12,B, with 

 plate 17,A, and plate 12,C with plate 17,E. 



Orifice: The shape of the zooecial orifice varies according to the 

 degree of frontal wall calcification and development of frontal oral 

 ledge and mucros. In the primary orifice the distal border is deeply 

 curved but less than semicircular. The proximal border is faintly 

 arched (pi. 12,C), but soon becomes obscured by the growth of the 

 frontal oral ledge, the two umbos or mucros, and the external avicu- 

 larium. The primary aperture is a bit smaller than the secondary 

 aperture and both are wider than long. Primary orifice length is 

 0.173-0.230 mm. (average 0.192 mm.) and width is 0.245-0.302 mm. 

 (average 0.269 mm.). Secondary orifice length is 0.202-0.266 mm. 

 (average 0.236 mm.), its width 0.259-0.389 mm. (average 0.320 mm.). 



Ovicells: Ovicells were not distinguishable externally. From the 

 internal aspect they are globular and hyperstomial. 



Types: Holotype, USNM 11227; paratypes, USNM 11228. 



Ecology: The species was collected by the 1947-48 expedition at 

 Station 234 in the Marguerite Bay area, Antarctica. Growing on 

 living colonies of C. margueritae were bits of sponge, a calcareous 

 worm tube, and some cyclostomatous bryozoans. 



Cellarinella rossi, new species 



Plate 13 



Diagnosis: Zoarium narrow, flattened, ribbonlike, bilaminate, 

 with some zoids opening along the edges also. Two mucros present, 

 the naked one being considerably closer to one corner of the orifice than 



