NO. 3 OSBURN : EASTERN PACIFIC BRYOZOA — CYCLOSTOMATA 779 



The species is related to H. reticulato-punctata (Hincks), but the 

 measurements are larger, the aperture shorter and wider, the preoral 

 area shorter and the cancellation of the front much more strongly 

 developed. 



Smitt described the species from Spitsbergen and carefully figured it 

 (plate 24, figs. 40 and 41), but I have not been able to find any other 

 record of its occurrence. 



Point Barrow, Alaska, Arctic Research Laboratory, 438 feet, G. E. 

 MacGinitie, collector, apparently rare. 



Microporella arctica (Norman), 1903 

 Plate 81, fig. 7 



Microporella arctica Norman, 1903:105. 



Porina ciliata Smitt, 1867:6 (part). 



Microporella ciliata var. arctica, Nordgaard, 1918:60. 



Zoarium encrusting stones and shells, heavily calcified, and the ectocyst 

 brown in color. The zooecia are much larger than those of M. ciliata 

 in all their measurements, 0.65 to 0.80 mm long by 0.40 to 0.65 mm 

 wide; the aperture 0.12 mm long by 0.15 mm wide; the ovicell averaging 

 0.40 mm in width. The frontal is a thick tremocyst with numerous small 

 pores which often become occluded in complete calcification ; inflated 

 with deep separating grooves and smooth, except occasionally there is a 

 minute umbo proximal to the ascopore. The aperture (except for size) 

 and the ascopore are similar to those of ciliata. Avicularia, rarely present, 

 are located near the lateral margin proximal to the aperture, the man- 

 dibles varying in length, the longer ones noticeably broader (more 

 ligulate) than those of ciliata. Spines are usually wanting but I have 

 noted 4 very minute (vestigial) ones on a few young marginal zooecia. 



The ovicell is hemispherical, delicately ribbed radiately in the young 

 stage but soon becoming very thick-walled and smooth, with a small 

 umbo distally situated on the top. 



Recorded previously by Smitt, Norman and Nordgaard from Spits- 

 bergen and northern Norway. The differences mentioned above indicate 

 that it should be separated from M. ciliata, and the following record 

 shows that it is a circumpolar species. 



Point Barrow, Alaska, Arctic Research Laboratory, 328 feet, G. E. 

 MacGinitie, collector. 



