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Show 410 ^ PP^ KMX E.- PALJ2ONT0LO0T. Fig. 4 b, the dorsal Valve of a larger individual, having six pli- - cations on each side of the mesial sinus* The surface is marked by distinct, undulating, concentric striae, which are agai$ crossed " by finer thread- like elevations, and which appear to have been the bases of short spines. Loe. Missouri River, near Weston, SPIRIFER TRIPLICATE, Hall, ( n. ep.) PLAII IL Fro. 5abc .• Shell subquadrangular; dorsal valve more gibbous than the ventral^ area nearly linear; beak of dprsal< valve small, acute, and closely incurved; mesial depression Bhallow in the upper part, but . becoming deeper and expanded tow. ard the base, . and produced in . front; eritire surface, including tlje mesial sinus, and elevation, covered with fine plications^ which, being simple in then: origin, soon dfvide into three, which ara continued to the base witbout further division. • . This species difters from the & itriatw, Sowprby, in its form,, and in the circumstance that the plications are less subdivided toward the margin of the shell.- ,:_ ' ' . Fig. 5 a, ventral* valve, and area of the - dorsal vajve. Fig. 5 br dorsal valve of the samp individual; Fig. 5 c, profile view of the same* The form is somewhat distorted by pressure.' •-../• '/.--' •'* Loe. Missouri River* above Western. ' CHONKTES VAKIOLATA, ( D'Orb. spr) De Koninck PIATB III. Fro. 1 ft b. > , ' ' ' This speoies bears the essential characteristics oL those figured ' and described by De Koninck, though it is larger than most of his - figures. The broad, scarcely defined mesial depression. Of th? dorsal valve gives a straight or slightly sinuous outline in, front. This fossil is . associated with several i f the preceding species, near Weston on the Missouri . River. **' |