NO. 3 OSBURN : EASTERN PACIFIC BRYOZOA CYCLOSTOMATA 629 



2. Plagioecia Canu, 1918, ovicell usually much broader than long, 

 not proliferated beyond the level of the ooeciopore ; ooeciostome terminal, 

 at or near the middle of the distal border ; one or more peristomes often 

 surrounded by the lateral prolongation of the ovicell. 



3. Diaperoecia Canu, 1918, the ovicell completes its development by 

 proliferating distally in advance of the ooeciopore and surrounds few 

 or many distal peristomes in the process; the ooeciostome, which repre- 

 sents the morphological distal end of the gonozoid, is usually located 

 somewhere near the middle or occasionally even near the proximal end 

 of the ovicell. 



4. Diplosolen Canu, 1918, miniature zooecia (zooeciules) present, 

 scattered among the normal tubules of the zoarium ; ooeciostome sub- 

 terminal at or near the middle; peristomes occasionally surrounded, 

 Diplosolen differs from Plagioecia in appearance only by the dimorphic 

 nature of the zooecial tubules. 



It is sometimes difficult to assign a species to one of the above genera, 

 owing to variation in the size and form of the ovicell and especially in 

 the occasional occurrence of ovicells as simple as those of Oncousoecia. 

 When these occur on the same zoarium with more highly developed 

 ovicells, the latter has been accepted as the proper generic association. 

 The simple ovicells usually occur on the older parts of the colony and 

 if only this form of ovicell is present the species would necessarily be 

 assigned not only to another genus but to a different family. A rather 

 exaggerated case of this is found in Plagioecia amhigua new species 

 (q. v.), bat examples may be found in other species of this genus and 

 also in Tubulipora. The enclosure of peristomes by the ovicell, on which 

 Canu (1918) based the genus Diaperoecia, is subject to much variation, 

 and this condition is also found to a greater or less extent in Plagioecia 

 and several genera of the Tubuliporidae. 



In spite of these variations, where a fully developed ovicell is present, 

 the position of the ooeciostome is usually diagnostic, median and terminal 

 or subterminal in Plagioecia, more centrally located in Diaperoecia, in 

 which genus the ovicell continues to develop distally beyond the ooecio- 

 stome. The ooeciostome must be considered the morphological distal end 

 of the gonozoid. 



Genus PLAGIOECIA Canu, 1918 



"The ovicell is a long transverse sack obliterating a certain number of 

 zooecial tubes and developed in the vicinity of the zoarial margins. The 

 ooeciostome is small, equal to or less than the zooecial diameter. The 



