NO. 1 OSBURN : EASTERN PACIFIC BRYOZOA CHEILOSTOMATA 23 



Zoaria encrusting, especially on the broader algae where the colonies 

 often coalesce to cover nearly the whole frond. The zooecia are of 

 moderate size, about 0.50 mm long by 0.20 to 0.25 mm wide, usually not 

 so regularly elongate-quadrate as in M. membranacea but otherwise re- 

 sembling that species. The walls are thicker and there is a narrow crypto- 

 cyst on the proximal and lateral sides which is irregularly serrated with 

 short laterally directed spinules ; there is often a somewhat longer spinule 

 at the proximal end. There is consistently a short hollow spine or pro- 

 tuberance at each distal corner, developed by the folding of the distal 

 rim; in older stages of calcification these spines may become closed at 

 the tips. The ancestrula is twinned like that of M. membranacea. 



Hincks' specimens were from Virago Sound, British Columbia; Rob- 

 ertson records it from Puget Sound to southern California ; O'Donoghue 

 lists it from numerous localities in British Columbia; Marcus found it 

 at several localities in Brazil, and Okada records it at a number of 

 places in Japan. The form which Hastings listed as A canthodesia ser- 

 rata from Balboa, Canal Zone, belongs elsewhere (see under Membrani- 

 pora hastingsae n. sp. ) . 



The name serrata as applied to this species is preoccupied by Mem- 

 branipora serrata IVIacGillivray, 1868:6, and a new name is necessary. 



Excessively abundant on the floating fronds of kelp and dredged on 

 a few occasions down to 10 fathoms. 



Membranipora tuberculata (Bosc), 1802 

 Plate 2, figs. 4, 5 and 6 



Flustra tuberculata Bosc, 1802:143. 

 Flustra tehuelcha d'Orbigny, 1839-46 :17. 

 Membranipora tehuelcha, Robertson, 1908:265. 

 Nichtina tuberculata, Harmer, 1926:208. 

 Nichtina tuberculata, Hastings, 1930:706. 

 Membranipora tuberculata, Osburn, 1947:9. 



This is the well-known "Gulfweed" bryozoan which Bosc described 

 as occurring "en immense quantite sur les fucus nageans sur I'Atlantique." 



The zoarium forms a white lace- work on Sargassum floating over the 

 wide oceans and occurs on attached algae along shore in warmer waters. 

 The zooecia are quadrangular, but shorter and wider than in M. mem- 

 branacea and the walls are much more heavily calcified. Characteristi- 

 cally there is a pair of tubercles at the distal corners, which appear to 

 be formed as folds of the distal rim as they are open and covered by 



