NO. 2 OSBURN: EASTERN PACIFIC BRYOZOA — CHEILOSTOMATA 471 



The zoarium is encrusting on anything that will afford attachment, 

 producing colonies of considerable size and sometimes rising in frills. 

 The zooecia are moderately large, 0.65 (0.50-0.80) mm long by 0.35- 

 0.45 mm wide, but extremes often exceed these measurements. The 

 frontal is a tremocyst with large infundibuliform pores. The aperture 

 is unusually large, 0.20 to 0.24 mm long by 0.18 to 0.20 mm wide, 

 the sides nearly parallel, the poster wider than the anter, shallow, with 

 the proximal border broadly arcuate ; the cardelles small. The operculum 

 fills the aperture, well chitinized, with a narrow sclerite scarcely separated 

 from the lateral border. The peristome is thin, slightly elevated and not 

 fused with the surrounding frontal. No spines; no external evidence 

 of an ovicell. Avicularia are usually wanting but occasionally there 

 is a small median, suboral one mounted on a small umbonate process; 

 I have found these only rarely on Atlantic specimens and at only two 

 Pacific stations but at one of the latter the avicularia are well distributed 

 over the colony. Otherwise there seems to be no difference in the zooecia. 



As this species was confused for many years with C. complanata 

 (Norman) and Hippodiplosia otto-mulleriana (Moll), the distribution 

 references are very uncertain, but at least it is known from the Mediter- 

 ranean Sea and the coasts of Morocco, Portugal and France, and in the 

 western Atlantic from Nova Scotia to North Carolina. It is especially 

 abundant on the shores of New England. On the Pacific coast earlier 

 writers did not mention it, and the only record is that of O'Donoghue 

 (1925:19) from Homer, Alaska. It is a fairly common species along the 

 coast of southern California, especially in the littoral zone. 



Hancock Stations: 1274-41, Hueneme, 29 fms; 1271-41, Anacapa 

 Island, 23 fms; 1208-40, Playa del Rey and 1644-48, White Point, near 

 San Pedro, along shore; 1221-41 and 1222-41, Newport Bay, shore; 

 and the writer has taken it along shore at Monterey Bay, Corona del 

 Mar and La Jolla, all in southern California. Farther south it has been 

 found at Station 1508-45, Sebastian Viscaino Bay, Lower California, 

 and at Salina Cruz, Oaxaca, Mexico, in shallow water (E. Yale Dawson, 

 collector). 



Genus WATERSIPORA Neviani, 1895 



Pachycleithonia Canu and Bassler, 1930:25. 



Frontal a tremocyst with numerous rather large pores. Ovicell endo- 

 zooecial, not evident on the surface. Aperture rounded, usually with a 

 broad rounded sinus and very strong cardelles. No spines, no avicularia. 

 Operculum with a chitinized border and a broad dark axial band which 



