Hydrotheca :: Hydrotheca (n.) One of the calicles which, in some Hydroidea (Thecaphora), protect the hydrants. See Illust. of Hydroidea, and Campanularian..
Hydrothermal :: Hydrothermal (a.) Of or pertaining to hot water; -- used esp. with reference to the action of heated waters in dissolving, redepositing, and otherwise producing mineral changes within the crust of the globe..
Hydrothorax :: Hydrothorax (n.) An accumulation of serous fluid in the cavity of the chest.