Plate 16 



Page 

 Figs. 1-5. Petraliella bisinuata Smitt, 1873 78 



1. Surface of the unilamellar zoarium; X 20. 



2. Inner face; X 20. The radicular septules (cribriform 



areas of Waters) are placed in the distal portion of the 

 cells. 

 Albatross Station D. 2405, Gulf of Mexico. 



3. Operculated and ovicelled zooecia; X 20. The lyrule 



and the cardelles are placed above the operculum. 



4. Structure of the frontal; X 85. 



5. Frontal viewed by transparency; X 20. The distal 



border of the operculum is visible. It is much chitin- 

 ized. The operculum has no proximal limit but 

 unites with the posterior walls of the compensatrix. 

 Albatross Station D. 2363, east of Yucatan. 

 6-11. Petraliella marginata, new species 80 



6. Unilamellar specimen, much calcified; X 20. The 



apertural avicularia are unequally developed and 

 sometimes deformed by the large frontal avicularia. 



7. Interior, X 20, showing the two condyles of rotation 



of the operculum, and the tremopores. 



8. Dorsal, viewed by transparency, X 20, showing the 



structure of the radicular septules (cribriform areas of 

 Waters) . 



9. Interior face of a unilamellar specimen; X 20. The 



radicular septules are large. 



10. Ovicelled zooecia much calcified; X 20. The sep- 



arating threads are quite salient. There are no fron- 

 tal avicularia and the apertural avicularia are very 

 large. 

 Albatross Station D. 2405, Gulf of Mexico. 



11. Unilamellar specimen, ovicelled; X 20. The large 



avicularium is lacking or little developed. 

 Albatross Station D. 2366, Gulf of Mexico, off Yucatan. 



12. Antropora pustulata, new species. (See also pi. 3, fig. 11.) 24 



The incrusting zoarium, X 20, showing the interzooe- 



cial pustules. 

 Albatross Station D. 2167, off Habana, Cuba. 



181 



