NO. 2 OSBURN: eastern pacific BRYOZOA CHEILOSTOMATA 397 



occluded. The primary aperture measures about 0.15 mm in width, 

 rounded distally but somewhat straighter on the proximal border where 

 it bears a broad but very short lyrula, often wanting. The peristome is 

 moderately high but does not rise much above the level of the thick 

 frontal wall ; on the proximal side it is connected with the avicularian 

 chamber. The avicularium is round or nearly so and often projects slightly 

 over the aperture ; its chamber is large and prominent, rising like a large 

 blunt umbo. It is roughened like the front and bears a few areolar pores 

 which are not conspicuous. The ovicell is rough like the frontal wall 

 and often bears an umbonate process. 



The species is widely distributed in northern waters. Hincks and 

 O'Donoghue recorded it from a number of localities in British Columbian 

 waters and Robertson from San Pedro, southern California. 



Not taken in Hancock dredgings. San Juan Island, Puget Sound, 

 (J. L. Mohr, collector) ; Canoe Bay, Alaska, Sta. 26-40 and 160-41, 

 and Alitak Bay, 100-40, (U. S. Alaska Crab Investigation) ; Punuk 

 Island, Bering Sea; Point Barrow, Alaska (G. E. MacGinitie, collector). 



Porella patens new species 

 Plate46, figs. 12-13 



Zoarium encrusting on shells and stones, unilaminar, white and shin- 

 ing. Zooecia moderate in size, 0.50 to 0.60 mm long by 0.30 to 0.35 mm 

 wide, usually arranged very regularly in parallel rows when on a smooth 

 surface; very distinct. The frontal is smooth, considerably inflated; 

 several areolar pores on each side, small and often difficult to see except 

 in prepared specimens, often occluded in secondary calcification. The 

 primary aperture is rounded distally and on the sides, the proximal 

 border slightly arcuate and without even a vestige of a lyrula; a small 

 pair of cardelles. The peristome is high, somewhat flaring on the sides 

 which are often raised into short lappets, low on the distal border 

 where there are 4 minute evanescent spines. The secondary aperture sub- 

 quadrangular in form, much larger than the primary aperture, widest 

 proximally, exposing the whole of the aperture. The suboral avicularian 

 chamber is small but extends laterally on both sides to the areolar pores ; 

 often with two pores (the areolar pores of the heterozooecium) ; the 

 rostrum high, shaped like a truncated cone and bearing on its tip a small 

 rounded avicularium. 



The ovicell is high, globular, smooth, the peristome forming a thin 

 lip above the orifice, about 0.20 mm wide and long. 



