NO. 2 OSBURN: eastern pacific BRYOZOA — CHEILOSTOMATA 465 



Cheilopora praelucida, Osburn, 1923 :1 Id ; 1936 :539. 

 Cheilopora praelucida, O'Donoghue, 1926:73. 

 ?Discopora sincera, Smitt, 1867:28. 



Encrusting or growing free, unilaminar or bilaminar. The zooecia 

 have much the aspect of C. praelonga, but the frontal is not so ventri- 

 cose and there are raised separating lines. The primary aperture is 

 rounded, or slightly quadrangular with rounded corners, and without 

 cardelles. The proximal tooth near the summit of the peristome is want- 

 ing in praelucida, and the umbonate proximal lip is not so prominent; 

 there is a forward extension of the distal lip but this also is smaller. 

 There are avicularia at one or both sides of the aperture, often wanting 

 and still more often degenerate to the extent that the avicularian aper- 

 ture is merely covered with a membrane. Hincks described it "avicula- 

 ria none," but his illustration (plate 4, fig. 1) shows one. In Labrador 

 specimens (Osburn 1912:283) the avicularian mandible is sometimes 

 well developed (see Osburn, plate 34, figs. 3 and 3c). Some zooecia 

 and some whole colonies are devoid of avicularia, some zooecia have 

 degenerate avicularia and others have them fully developed. 



The ooecium was not found by Hincks and O'Donoghue. I have 

 seen it only once, in a Labrador specimen (Osburn, 1912, plate 34, 

 fig 3a). It is hemispherical, deeply set in the base of the succeeding 

 zooecium, endozooecial, the exposed surface irregularly perforated. 



In my opinion praelucida is merely a variety of sincera Smitt, though 

 the avicularium is more pointed and the ovicell, if one may judge from 

 Smitt's imperfect figure, is larger and more rounded. Without the 

 opportunity to make a direct comparison it seems better to keep them 

 separate for the present. 



Hincks described the species from Houston Stewart Channel, British 

 Columbia, and later discussed it in material from the Gulf of St. 

 Lawrence. O'Donoghue reported it from Brotchie Ledge, Victoria, 

 British Columbia. Osburn has listed it from Labrador, Hudson Strait 

 and Bay, and Dolphin and Union Strait in the Arctic Ocean. C. sincera 

 has been reported from Spitzbergen, Finmark, Greenland and as far 

 west as Dolphin and Union Strait. 



