3.—Subgenus Fossacallista nov.

Genotype: Paradione (Notocallista) parki Marwick. Awamoan (Low. Miocene), New Zealand.

Shell rather small, suboval. Lunule defined by an incised line. Surface shining, finely concentrically grooved, tending to be smooth medially. Hinge like Notocallista, but the left posterior cardinal tends to be less closely welded to the nymph, some specimens showing a well-defined groove between the two. Ligament deeply sunk with high walls which, however, are scarcely raised above the well-marked posterior marginal ridge. Pedal retractor confluent with the anterior adductor. Pallial sinus moderate, ascending, rounded at the end.

Readily distinguished from Notocallista and Striacallista by the sunken ligament, confluent pedal retractor, and rounded pallial sinus. In these characters it agrees with Chionella, and relationship to this group is further indicated by the shallow groove that in some specimens separates the left posterior cardinal from the nymph. Thus