Definify.com

Webster 1913 Edition

Noun.

[Pref.

pro-

for +

siphon

(Zool.)

A minute tube found in the protoconch of ammonites, and not connected with the true siphon.

prosiphon ‎(plural prosiphons)

(zoology) A minute tube found in the protoconch of ammonites, not connected with the true siphon.