NO. 2 OSBURN: eastern pacific BRYOZOA CHEILOSTOMATA 517 



Kadiak and Juneau, Alaska. Osburn (1921:451) reported it from the 

 stomach of a king eider duck at St. Georges Island, Bering Sea. 



Abundant at Point Barrow, Alaska, down to 25 fms, Arctic Research 

 Laboratory, G. E. MacGinitie, collector. 



Family Mamilloporidae Canu and Bassler, 1927 



"Hexapogona with orbicular zoarium without pit. The cells are 

 juxtaposed. The proximal border of the apertura is oriented toward the 

 apex. The ovicell has a special interzooecial cavity and is closed by the 

 operculum." (Canu and Bassler, 1930:474.) 



Canu and Bassler placed this family in a new suborder Hexapogona 

 which apparently cannot be maintained, at least on the basis of the 

 short description, "The ancestrula engenders six zooecia." The family 

 Mamilloporidae, however, is quite satisfactory, including several related 

 genera, of which only Mamillopora occurs in our collections. 



Genus MAMILLOPORA Smitt, 1873 



The zoarium is free, cupuliform, but varying from short-conical to 

 nearly flat, the outline rounded. The zooecia are erect, showing only 

 the aperture and broad peristome on the frontal surface. The frontal 

 avicularia are interzooecial, as their chambers are continued to the dorsal 

 side parallel to the zooecial chambers ; avicularia occur also on the dorsal 

 side of the zoarium. The ovicell is hyperstomial and closed by the 

 operculum, deeply embedded; as it develops before the succeeding 

 zooecium is completely formed the distal zooecium is distorted to con- 

 form to the ovicell at the frontal surface. Genotype, Mamillopora cupula 

 Smitt, 1873. 



Mamillopora cupula Smitt, 1873 



Plate 64, figs. 10-11 



Mamillopora cupula Smitt, 1873 :33. 



Mamillopora cupula, Canu and Bassler, 1928: 153; 1930:45. 



Mamillopora cupula, Hastings, 1930 :733. 



Mamillopora cupula, Osburn, 1947 :46. 



Zoarium free, cupuliform or saucer-shaped, the outline round. The 

 zoaria are quite erect, their cavities parallel, the frontal surface limited 

 to the aperture and the broad peristome which is usually provided with 

 a series of low tubercles. The aperture is somewhat variable in size and 

 form, averaging about 0.13 mm wide by 0.17 mm long, rounded back 



