clepsine

from The Century Dictionary.

• noun A genus of the order Hirudinea, including some of the lower forms of leeches, in which the sinus and other vessels form a continuous system of cavities containing blood, and in which the segmental organs open into the sinuses by ciliated apertures. It is the typical genus of the family Clepsinidæ. C. bioculata is an example.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Zoöl.) A genus of fresh-water leeches, furnished with a proboscis. They feed upon mollusks and worms.