CHARACTERISTIC DEEP-SEA TYPES. BRYOZOA. 



81 



is one of the most common of the West Indian bryozoans inside 

 the two-hundred-fathom line, but extending to nearly 500 fath- 



Fig. 331. Tessadroma boreale. 



Fig-. 331 a. Tessadroma bo- 

 reale. Magnified. (Smitt.) 



oms. Equally common is Tessadroma bo- 

 reale (Figs. 331, 331 ), a species not in- 

 frequent on the east side of the Atlantic 

 from Spitzbergen to the Azores. 



A very common incrusting type found 

 growing on shells and corals is Hippothoa 

 biaperta (Figs. 332, 332 a), which goes 

 back to the tertiary. 



A species of Cellepora is very abundant 





Fig. 332 a Hippothoa 

 biaperta. Greatly magni- 

 fied. (Smitt.) 



Fig. 332. Hippothoa bia- 

 perta. ^. 



