NO. 1 OSB URN : EASTERN PACIFIC BRYOZOA CHEILOSTOMATA 115 



the opesia, is granulated like the border. The opesia is only slightly larger 

 than the operculum, which is free from the border at all points; semi- 

 elliptical, widest at the proximal border which is transverse or slightly 

 arcuate and often with a minute opesiular angle at the proximal corners. 

 The operculum is thin with a narrow bordering sclerite, somewhat more 

 than a semicircle, straight on its proximal border where it is attached 

 to the frontal membrane a short distance in advance of the margin of the 

 cryptocyst. The mural rim is continued broadly around the aperture and 

 often bears two short stout tubular spines. There are no avicularia on 

 our specimens and Smitt does not mention them. Dietellae are present, 

 one large distal and several smaller lateral ones, all quite conspicuous 

 at the edges of the zoarium. 



The ovicell is hyperstomial, prominent, rounded, 0.30 mm in width, 

 the ectooecium thick, granulated like the frontal and continuous with 

 the frontal wall of the succeeding zooecium ; it is not closed by the 

 operculum. 



Our specimens appear to agree in every detail with Smitt's illustra- 

 tions (PI. 21, figs. 17-19), though he does not mention the dietellae. His 

 specimens were from Spitsbergen or at least north of Norway, "Fran 

 1868 ars Spetsberg-expedition," and I have not been able to find a more 

 recent reference to the species. 



The generic relationship of this species may be questioned because of 

 the absence of dietellae and the somewhat longer opesia in the fossil 

 species which have been allocated in this genus, but all of the other 

 characters seem to conform absolutely. No other recent species is known, 

 though Canu in his description of the genus did mention Membranipora 

 trifolium var. minor Hincks which, however, is a synonym of Amphibles- 

 trum papillatum Busk. 



Type, AHF no. 49. 



Point Barrow, Alaska, 18 fms on shells, G. E. MacGinitie, collector, 

 Alaska Research Laboratory. Evidently it is an arctic species with circum- 

 polar distribution. 



Division IV PSEUDOSTEGA Levinsen, 1909 



The cryptocyst covers most of the frontal area. There are no spines 

 or pores; the avicularia are vicarious (replacing zooecia in the series), 

 with usually a transverse pivot. The ooecia are embedded in the base of 

 the succeeding zooecia and open by special pores distal to the aperture. 

 The group is a comparatively small one, with only a few genera. 



