streptoneura

from The Century Dictionary.

• A branch of anisopleurous Gastropoda, in which the long loop of visceral nerves embracing the intestine is caught and twisted into a figure-of-8 by the torsion which the animal undergoes in its development.

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

• noun plural (Zoöl.) An extensive division of gastropod Mollusca in which the loop or visceral nerves is twisted, and the sexes separate. It is nearly to equivalent to Prosobranchiata.