254 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



PETRALIA JAPONICA Busk, 1884 



Plate 23, figs. 1-3 



1909. Lepralia japonica Waters, Bryozoa of the Sudanese Red Sea, Linnean 

 Society Journal, Zoology, vol. 31, p. 149, pi. 13, figs. 10-12. (Bibli- 

 ography, geographic distribution.) 



1921. Petralia japonica Marcus, Bryozoen, Results of Swedish scientific 

 expeditions to Australia, Kungl. svenska Vetenskaps-Akademiens 

 Handlinger, vol. 61, No. 5, p. 26, pi. 1, figs. 16, 17; pi. 2, fig. 3. (Bibli- 

 ography.) 



Fig. 104. — Genus Petralia Levinsen, 1909 



A-G. Petralia japonica Busk, 1884. A. Zoarium, one-half natural size (after 

 Marcus, 1920). B. Zooecia, X20. The lowermost zooecium to the left shows 

 a hollow, from which the whole ovicell has been removed; the uppermost to the 

 right shows on the other, hand an ovicell with the frontal wall removed (after 

 Levinsen, 1909). C. Zooecia, X25, with ovicells and one broken-down ovicell. 

 D. Avicularian mandible, X85. (C, D. After Waters, 1909.) E, F, G. Oper- 

 cula, X85. (E. After Levinsen, 1909. F. Waters, 1909. G. Canu and 

 Bassler.) 



Zooecia 



\Lz 

 lz~ 



= 1.25 mm. 

 0.70 mm. 



Measurements. — 



. iha^0A5 mm. 



Aperture] fe=04()mm 



Structure. — The poster is wider than the anter; they are separated 

 from each other. On the interior this separation is indicated by two 

 lateral condyles altogether invisible exteriorily. The frontal is a 

 tremocyst supported by a perforated olocyst. 



The structure of the ovicell is analogous to that of the frontal, but 

 the tremopores are finer. 



