NO. 3 OSBURN : EASTERN PACIFIC BRYOZOA CYCLOSTOMATA 639 



I have observed a number of cases of similar ambiguity among the 

 Diastoporidae and Tubuliporidae, but never quite to this extent. Pre- 

 sumably all such cases may be interpreted as examples of the repetition 

 of ancestral characters and therefore useful in tracing the evolution of 

 the group. At the same time they present a problem in identification, 

 for if only the simple ovicell is present the species must necessarily be 

 assigned to a different genus and even a different family than if the 

 expanded ovicell is developed, according to Canu's analysis. 



? Plagioecia lactea (Calvet), 1903 



Diastopora lactea Calvet, 1903:163; 1907:466. 

 Plagioecia lactea, Canu and Bassler, 1930:48. 



The zoarium is flat and discoidal, with a narrow basal lamina, and 

 is attached by a peduncle. The zooecial tubules are immersed for most 

 of their length, their surfaces rather coarsely cross-striated and punc- 

 tured. The peristomes are moderately short, semi-erect and well sepa- 

 rated. Occasional apertures are closed with a lamella with a central 

 minute tubule. The orifices are round or slightly elliptical and measure 

 about 0.08 mm; the peristomes 0.10 to 0.12 mm in diameter, depending 

 on the amount of calcification. 



While no ovicells have been noted in the Hancock specimens, the 

 descriptions and figures given by Calvet and Canu and Bassler, and 

 measurements by the latter are all in agreement. 



Recorded by Calvet from the Gulf of Gascony at 300 meters and 

 from Cape Spadel, Morocco, at 717 meters, and by Canu and Bassler 

 from the Galapagos Islands, Albatross Sta. D.2813, at 40 fms. 



Hancock Station 143-34, off Wenman Island, Galapagos, 1°23'10"N, 

 91°48'45nV, at 100 to 150 fms. 



Genus DIPLOSOLEN Canu, 1918 



Diplopora Jullien, 1903:115 (preoccupied by Gumbel, 1866). 



Interspersed among the autozoids are nannozoids or reduced indi- 

 viduals, irregularly distributed, their minute peristomes shorter than 

 those of the normal tubules and often inconspicuous. The ovicell is a 

 prominent swelling, usually surrounding a number of peristomes; the 

 ooeciostome smaller than the peristomes, short, erect and isolated. Geno- 

 type, Tubulipora obelia Johnston, 1838. 



Older authors placed the species under Tubulipora, Berenicea and 

 Diastopora, but the constant presence of nannozoids, the function of 

 which is unknown, appears sufficient for generic standing. 



