NO. 1 OSBURN: EASTERN PACIFIC BRYOZOA CHEILOSTOMATA 33 



0.40 (0.26 to 0.50) mm. Opesia variable in form and size (0.25 to 0.50 

 mm long by 0.25 to 0.45 mm wide), irregularly rounded or ovate and 

 occupying approximately the distal half of the front. The mural rim flares 

 outward on the sides over the bases of the adjoining zooecia. The proxi- 

 mal half, more or less, of the front is occupied by the extensive gymnocyst. 

 When first formed this is smooth but soon a series of ribs (4 to 7 in 

 number, with a median one which forms a sort of keel) grows inward 

 from the border to become attached to the median keel ; these ribs are 

 apparently developed from the surface of the gy^mnocyst, as a part of it, 

 and while they may have some resemblance to the costae of the cribri- 

 morphs, they are in no sense homologous. There is no evidence of a crypto- 

 cyst. The frontal membrane is somewhat chitinized and the operculum 

 (about 0.20 mm broad) has a heavier brown border. 



The distal border of the g}'mnocyst bears a peculiar large, sessile, 

 median, transverse avicularium with a short-triangular mandible which 

 is hooked at the tip. There are no ooecia; no spines; no dietellae. 



Robertson described the species from Yakutat, southern Alaska, and 

 apparently it has not been noted since. 



Our specimens are from Yakan Point, Queen Charlotte Islands, 

 British Columbia, low tide. Dr. E. F. Ricketts, collector, three colonies. 



Genus CUPULADRIA Canu and Bassler, 1919 

 The name Cupularia (Cupulaire Lamouroux, 1821), used to include 

 species of Cupulndria and Discoporella for many years, has been shown 

 by Hastings (1930:717) to be untenable. In 1919:77 Canu and Bassler 

 established the genus Ciipuladria, with C. canariensis Busk as the geno- 

 type, to include the membraniporid species with a wide open front. 



Gupuladria canariensis (Busk), 1859 

 Plate 3, figs. 2 and 3 

 Membranipora canariensis Busk, 1859:66. 

 Cupuladria canariensis, Hastings, 1930:714. 



Zoarium free, unilaminar; shaped like a cup or saucer, varying 

 greatly in this respect, sometimes almost plate-like, at other times quite 

 cupuliform; usually quite circular but occasionally elliptical or distorted. 

 The zooecia are rhomboidal, as a rule very regularly arranged, each with 

 a long chitinous flagellum at the distal end. The opesia is large, without 

 any trace of a horizontal crj-ptocyst. The walls are thin and high, with 

 a narrow descending cryptocj'St which is distinctly granulated but which 

 never bears spinules. The vibracula are very long and rather stiff and 



