The Collaborative International Dictionary of English v.0.48:
Coenurus \C[oe]*nu"rus\, n. [NL. fr. Gr. koino`s common + o'yra`
tail.] (Zool.)
The larval stage of a tapeworm (T[ae]nia c[oe]nurus) which
forms bladderlike sacs in the brain of sheep, causing the
fatal disease known as water brain, vertigo, staggers or gid.
[1913 Webster]
Note: This bladder worm has on its surface numerous small
heads, each of which, when swallowed by a dog, becomes
a mature tapeworm in the dog's intestine.
[1913 Webster]