Plate XVIII. 
Fig. 1... Leperditia: nicklesi;m. sp). 2 1:5 |) )\ae ee 200 
Ia, 16 and Ic, side, anterior, and ventral views, x 28, of a left valve. 
Columbia, Ill. 
1d, interior of another left valve; narrower in front ; x 28. 
Ie, sectional view of ventral portion of carapace, showing method 
of overlap. 
Fig. 2, Kirkbya @ Barychilna) costata (\icCoy) aaa 208 
2a and 26, side and edge views of a valve of this species, x 20. 
Columbia, Ill. 
Fig: 3. Kirkbya venosa, n. sp. 9.207. 202) er 208 
3a, side and posterior views of a right valve, x 28; from Chester 
group, near Grayson Springs, Ky. 
Figs. 4 and 5. Kuirkbya oblonga, Jones and Kirkby........ 206 
4a and 44, side and end views of a symmetrical valve of this species, 
x 28. Chester, Il. ‘ 
sa and 54, side and end views of an unsymmetrical right valve, 
x 28. Near Grayson Springs, Ky. 
Fig.,'6. ‘Kirkbya jindahli, nm.’ sp, 925.2) -02 2 207 
6a, 66 and 6c, side, ventral, and posterior views, x 20, of a medium 
sized right valve. Columbia, III. 
Fig. 7: Beyrichia simulatnix, nm: sp... (0). 3 205 
72 and 74, side and posterior views of a left valve, x 28. Near 
Grayson Springs, Ky. 
Fig. 8. Kirkbya tricollina, Jones and Kirkby ea Weer ok 207 
8a and 84, side and end views, x 28, of a (? right) valve of this spe- 
cies. Near Grayson Springs, Ky. 
