Minulites) planulata, Craspe grate-acute; posterior dorsal margin oblique, rectilinear, ex- tremity acute, rounded; basal margin regularly arched; sub- acute. Greatly... Purlacki... in major county. Halle Mice, p. 50 Hystricoma) plana, Sulfhyminitial compressed; posterior dorsal margin rectilinear, extremity rounded. I was fortunate enough to obtain two fine casts of the hinge of this bivalve, with the teeth remarkably well represented, occur in a sand- stone of Salin mbr. series, near Rome, Canada Cr. p. 51