PLATE XV. 



[Proc. Wash. Acad. Sci., Vol. Ill, Pi. XXVI.] 



Fig. :. Thuiaria coei Nutting. Part of brancli, showing hydrothecse and 

 gonangia (enlarged). 



2. L-iteral view of hydrotheca (enlarged). 



3. Single gonangium (enlarged). 



4. Tkuiayia costata Nutting. Part of main stem, showing origin of 

 branches (enlarged). 



5. Front view of terminal branches (enlarged). 



6. Two pairs of hydrothecae (greatly enlarged). 



7. 8, 9. Gonangia (enlarged). 



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