PLATE XL 
Figs. lA, B. Monocyrtoceras cf. lentidilatatiim Foerste. A, lateral 
view; B, ventral view. Neither presents the outline of the aperture, 
although the full height of the living chamber appears to be retained by 
the specimen. From Wauwatosa, Wisconsin, in the Racine member of 
the Niagaran. Specimen No. 2312, in Museum of Comparative Zoology, at 
Harvard University. 
Fig. 2. Poterioceras fiisiforme (Sowerby). Lateral view. Copied from 
Foord, Carb. Ceph. Ireland, 1897, pi. 15, fig. 2b. From the Carboniferous. 
