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. 
oms. Equally common is Zessadroma bo- 
reale (Figs. 331, 331 a), 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.) 
Magnified. (Smitt.) 
Fig. 332. —Hippothoa bia- 
perta. 4. 
