NO. 2 OSBURN : EASTERN PACIFIC BRYOZOA CHEILOSTOMATA 351 



of areolar pores and occasionally a few additional ones; when young 

 the frontal may be slightly costate around the sides, but this is lost with 

 increasing calcification, and frequently there is a low, rounded umbonate 

 swelling on either side of the aperture. There is a thin shining ectocyst. 

 The aperture is longer than broad, varying but averaging about 0.15 

 mm long by 0.13 mm wide, the sides nearly straight, the cardelles set 

 far back, the poster very broad and shallow, the proximal margin nearly 

 straight. The operculum fills the aperture, well chitinized and a sinuous 

 sclerite runs forward from the cardelle on either side. The vestibular 

 arch is delicately beaded. The peristome is low and thin, sometimes with 

 2 to 4 small spines which are lost very early, and the thick frontal sub- 

 merges both aperture and peristome at the bottom of a deep tube. Proxi- 

 mal to the aperture and a little to one side is a small avicularium (often 

 wanting) with a semicircular mandible which is directed laterally; the 

 chamber of the avicularium appears like an asymmetrical umbo and, 

 with the thickening of the frontal it is often submerged to open into 

 the secondary aperture. Similar small avicularia frequently appear else- 

 where on the front. Dietellae are present. 



The ovicell has not hitherto been noticed. It is high, globular, 

 imperforate and smooth but soon becomes covered by the pleurocyst 

 of the adjoining zooecia ; 0.26 mm wide. 



The species was described by Hincks from Houston Stewart Channel 

 and Cumshewa, later listed by O'Donoghue from Northumberland 

 Channel, British Columbia. 



Not taken in the Hancock dredgings, but collected at Middle Bank, 

 Puget Sound, by Dr. John L. Mohr, several colonies. 



Hippoporella rimata new species 

 Plate 45, figs. 6-7 



Zoarium encrusting, white and shining. Zooecia small, 0.30 to 0.45 

 mm long by 0.25 to 0.30 mm wide, irregularly hexagonal ; frontal thick, 

 porcellanous, shining and with numerous comparatively large granules 

 which are conspicuous even in the young. The aperture measures about 

 0.09 mm wide by 0.08 mm long, the anter rounded back to the prominent 

 cardelles, behind which a very shallow poster extends the full width 

 of the aperture with its proximal border straight or very slightly arched ; 

 the vestibular arch is delicately beaded. The operculum is well chiti- 

 nized, yellowish, with the sinuate sclerites separated from the border. 

 The peristome rises but little above the thick front, its rim provided 

 with 4 or 5 short spines; notched on the proximal border to produce a 



