NO. 3 OSBURN : EASTERN PACIFIC BRYOZOA CYCLOSTOMATA 693 



curve outwards, and although at the growing tip these tubes are parallel 

 to the axis of the branch, when adult they curve almost at right angles 

 with the axis of the branch and the apertures open laterally, the larger 

 zooecial apertures being surrounded with a circle of small interstitial 

 openings." 



Borg (1932, 1933 and 1944) has made a very detailed study of the 

 anatomy, development and the brood-chambers of recent species of 

 Heteropora and related genera. He rejects the genus Tretocycloecia 

 Canu, 1918a :346, erected to include the species with ovicells and leaving 

 the old genus Heteropora for those in which the ovicells are unknown, 

 as "inadmissible." 



Heteropora magna O'Donoghue, 1923 

 Plate 73, fig. 13 



Heteropora magna O'Donoghue, 1923:14. 

 Tretocycloecia magna, O'Donoghue, 1926:29. 

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

 Heteropora magna, Borg, 1933:326. 

 Tretocycloecia pelliculata, Canu and Bassler, 1922:110. 



"Zoarium stout, densely branched, more or less spherical in outline; 

 distal ends of autozoids not or only slightly protruding; apertures of 

 kenozoids mostly open, but sometimes, in older portions of the zoarium, 

 closed." (From Borg's key, 1933:284). 



The encrusting base gives rise to erect cylindrical stems, 3 to 5 mm in 

 diameter, which branch dichotomously while retaining their original 

 thickness, but a little swollen at the tips. The zoarium thus has a more 

 or less spherical form, except when modified by the substratum. There 

 is occasional anastomosis of the branches, "but not so frequently as in 

 H. pelliculata (now H. pacifica Borg, q.v.) and the colony as a whole 

 has a much more stout and compact appearance . . . and may measure 

 100 by 70 mm." (After O'Donoghue). Zoarium purplish-brown in 

 color. 



Ovicells were not observed by either O'Donoghue or Borg. They are 

 large irregular areas on the sides of the branches near the tips and par- 

 tially surrounding the branches, only slightly elevated, but conspicuous 

 because of the closure of the kenozoids ; appearing as a complete, calcified, 

 thin, whitish cover of the brood-chamber, with the exception of the 

 peristomes of the autozoids which are not displaced. The peristomes 

 are more prominent than elsewhere on the zoarium and are often slightly 



