NO. 3 OSBURN : EASTERN PACIFIC BRYOZOA — CYCLOSTOMATA 695 



in more sheltered areas the peristomes are very evident. The apertures 

 are about 0.17 mm in diameter, in older parts of the colony they are 

 usually closed. The kenozoids never project above the surface and are 

 usually closed except tow^ard the growing ends of the branches. Brood- 

 chamber not knov^^n. 



While this species may have a considerable range along the Pacific 

 coast from Alaska to California, as suggested by O'Donoghue, the only 

 positive records are those of the material studied by Borg, Vancouver 

 Island region to Middleton Island, southern Alaska, down to a depth 

 of 25 meters. 



There is in the Hancock collection a very small fragment labelled 

 Heteropora pelliculata Waters by Robertson, from "San Diego, Cali- 

 fornica," which may belong to H. pacifica as the zoids have the same 

 measurement, 0.17 mm. There are also several much worn fragments 

 from Hancock Station 1278-41, off San Miguel Island, southern Cali- 

 fornia, at 35 fms, which present the same zooecial measurements and 

 with stems 2 to 3 mm in diameter, which may belong here. But none 

 of these specimens is in condition for determination beyond the genus. 



There are also several much worn fragments from Hancock Stations 

 143-34, Wenman Island, and 170-34, Chatham Island, Galapagos 

 Islands, which present about the same measurements, but which are not 

 identifiable beyond the genus Heteropora. 



Heteropora alaskensis (Borg), 1933 



Plate 73, figs. 10, 11, and 12 



Heteropora pacifica var. alaskensis Borg, 1933:325. 

 Heteropora pelliculata, Robertson, 1910:258 (part). 

 "i Heteropora pelliculata, O'Donoghue, 1923:14 (part). 



The zoarium is very irregular and much smaller than that of H. 

 magna or H. pacifica. Our largest colony measures 16 mm in height by 

 25 mm in width, with 16 branches which average about 2 mm in 

 diameter, but most of the 10 colonies are shorter and more compact; 

 the branches, beyond a bifurcation, are 2 to 4 mm long (in one case 

 7 mm) ; only a few cases of anastomosis occur. 



The essential characters which differentiate this form from other 

 species of Heteropora are: (1) the peristomes of the autozoids project 

 to a marked degree on the branches all the way up to the margins of 

 the cancellated tops, and on older basal branches they still rise slightly 

 above the level of the zoarial surface; diameter of apertures 0.14 (0.13 

 to 0.17) mm; (2) the kenozoids are covered and closed over the whole 



