HYDROIDS. 103 
detected by Agassiz on one of his cruises to the reefs of Flori- 
da. The coral-making Hy 
rdroids have been named /7ydroco- 

HYDRALLMANIA FALCATA, 
ralline. The group includes also, as Moseley first showed, the 
Stylasteridz mentioned on page 70 and other related species. 
The corals of the Milleporz are solid and stony, as much 
so as any in coral seas. They have generally a smooth sur- 
