434 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 14 



Genus GYSTISELLA Canu and Bassler, 1917 



Zoarium erect, branching, flabelliform, bilaminate. The frontal is 

 an olocyst with few areolar pores ; a large elongate avicularium chamber 

 covers most of the front, with two large pores in its proximal end a little 

 distal to the preceding aperture, and its mandible is semicircular and 

 perpendicular to the apertural plane. No lyrula, no oral spines, cardelles 

 present. Ovicell hemispherical, smooth and imperforate. Genotype, Es- 

 chara saccata Busk, 1856. 



A short, broad lyrula is present in some species. The avicularian 

 chamber is unique in that it extends the full length of the front of the 

 zooecium, originating from proximal instead of lateral pores. 



Gystisella saccata (Busk), 1856 

 Plate 51, figs. 4-5 



Eschara saccata Busk, 1856:33. 

 Gystisella saccata, Osburn, 1923 :10D. 



A common high northern species, growing in erect bilaminate folds 

 to a height of 50 mm. The zooecia are moderately large, averaging 

 about 0.75 mm long, quincuncial in arrangement, the frontal thick, 

 smooth and shining, with one or two pores at the proximal end (visible 

 only after removal of the ectocyst). Most of the front is covered by a 

 large and elongate avicularian chamber which extends from the proximal 

 pores to overhang the aperture ; the distal end is vertical to the plane 

 of the aperture and is occupied by a large semicircular mandible. The 

 primary aperture is so deeply hidden below the avicularium and the high 

 peristome that it can be seen only on young zooecia; it is a little more 

 than a semicircle, with a straight proximal border and without lyrula 

 or cardelles; 0.18 to 0.20 mm wide. 



The ovicells in the young stage are globular, prominent, smooth 

 except for faint radiating striae but in older parts of the colony they 

 become embedded and covered by the thick crust ; width and length 0.30 

 to 0.35 mm. 



This species was confused for many years with C. elegantula (d'Or- 

 bigny) until Waters, 1900:81, pointed out the differences. It is widely 

 distributed in the arctic region and Osburn (1923, Canadian Arctic 

 Exped.) recorded it as far west as Icy Cape, Alaska. 



Point Barrow, Alaska, G. E. MacGinitie, collector, Arctic Research 

 Laboratory. 



