prosobranch i at a

pl. [Pref. proso-, and 1. Zool.: An order of Gasteropod a, founded by Milne-Edwards, embracing the Pectini, Scuti-, Cyclo-, and Tubulibranchiata of Cuvier. The gills are pectinated and in advance of the heart; the soft parts are protected by a shell, into which the animal can usually withdraw its body; eye-pedicels and tentacles on same stalk; sexes distinct. There are two divisions of the order, Holostomata and Siphonostoma (q. v.). 2. Palæont.: From the Silurian onward. pros-o-brăn-chi-ate, a. [PROSOBRANCH I AT A.] Of, pertaining to, or characteristic of the Proso branch i at a.