PLATE Vb. 
(Figures 3, 4, 8, 15-21, 27-39, by R. P. Whitfield; 9, 22-26, by JG. ElIJIONS; 10-14, by J 0. McConnell.) 
Legend. A- Deltidium. 
j. Cardinal process, 
t. Teeth. 
b. Sockets. 
c. Crura, 
s. Septum. 
p. Pedicle muscle. 
a. Anterior adductor impressions. 
a / . Posterior adductor impressions, 
r. Anterior diductor impressions. 
v'. Posterior diductor impressions, 
o. Ovarian markings, 
v. Vascular markings. 
PLATYSTROPHIA, King. 
Page 200. 
Orthis biforata, Schlotheim, var. lynx, von Eichwalcl. 
Fig. 1. A cardinal view of an average individual; showing the area and delthyrium of each valve. (The 
lines limiting the delthyrium are too strongly defined.) 
Fig. 2. An exterior of the brachial valve of a smaller specimen. 
Fig. 3. The interior of a brachial valve ; showing the narrow, linear cardinal process, large crural plates 
and the quadripartite impression af the adductor muscles. 
Fig. 4. The interior of a large pedicle-valve. The apical portion of the shell has been absorbed, being 
the usual condition in old shells of this form, thus exposing the impression of the pedicle-muscle. 
The specimen also shows the compact form of the muscular scars, the vascular trunks and ova¬ 
rian markings. 
Hudson River group. Cincinnati, Ohio. 
Orthis biforata, Schlotheim, var. laticosta, Meek. 
Figs. 5, 6, 7. Profile, brachial and front views ; showing the high median fold characterizing this form. 
Fig. 8. The interior of a brachial valve. 
Fig. 9. An enlargement of the delthyrial portion of the brachial valve. The obsolescent character of 
the cardinal process is probably due, in part, to reabsorption. 
Hudson River group. Cincinnati, Ohio. 
Orthis biforata, Schlotheim. 
Fig. 10. The exterior of the pedicle-valve. The surface is covered with fine granules which, however, are 
very rarely retained (and almost never visible in ordinary specimens). X 3. 
Trenton limestone. Trenton Falls, N. Y. 
For further illustration of Platystrophia, see Davidson, Silurian Brachiopoda, pi. xxxviii, figs. 11- 
25; Palaeontology of Ohio, Volume I, plate x. 
BILOBITES, Linne. 
Page 204. 
Orthis biloba, Linne. 
Figs. 11, 12, 13, 14. Views; showing the variation in form in this species. Fig. 14 is of the type described 
by Ringueberg as O. acutiloba. X 3. 
Niagara group, fjockport, N. Y. 
Orthis varica, Conrad. 
Figs. 15, 16, 17. Three views of the same specimen. X 2. 
Fig. 18. The interior of the pedicle-valve ; showing the area, delthyrium, teeth and outline of the muscu¬ 
lar area. X 4. 
Fig. 19. The interior of the brachial valve; showing the cardinal process, the great crura, large muscular 
area, and the pectinated surfaces of marginal contact. X 5. 
Lower Helderberg group. Near Clarksville. N. Y. 
