PLATE VI. 
(Figures 1-34, by R. P. Whitfield.) 
Legend. A. Cardinal area, 
t. Teeth. 
1/. Sockets, 
d. Dental lamellae, 
c. Crura. 
s. Median septum, 
j. Cardinal process. 
p. Pedicle-area, 
a. Anterior adductor scars. 
a,'. Posterior adductor scars, 
r. Anterior diductor scars. 
v'. Posterior diductor scars, 
v. Vascular markings, 
o. Ovarian markings. 
RHIPIDOMELLA, CEhlert. 
Page 208. 
Orthis hybrida, Sowerby. 
Figs. 1, 2, 3. Three views of an average individual of the American form referred to this species. 
Fig. 4. The interior of the brachial valve. The character of the diductor muscular scars is here incor¬ 
rectly represented, the impression being quadripartite and not flabellate. 
Fig. 5. The interior of the pedicle-valve ; showing the expanded muscular scars. 
Niagara group. Lockport, IV. Y. 
For further illustration, see Davidson, Silurian Brachiopoda, plate xxvii, figs. 1-9 ; Hall, Palaeon¬ 
tology of New York, Volume II, plate lii, fig. 3; Twenty-eighth Rept. N. Y. State Mus. Nat. 
Hist., pi. xxi, figs. 18-25, 
Orthis Penelope. Hall. 
(See Plate VI a, fig. 10.) 
Figs. 6, 7, 8. Three views, giving the external characters of a normal mature individual. 
Fig. 9. The interior of a brachial valve ; showing the articulating apparatus. The muscular area is quad¬ 
ripartite rather than flabellate. 
Fig. 10. The interior of a small pedicle-valve. 
Fig. 11. Similar view of an older shell. 
Fig. 12. The interior of a pedicle-valve, which shows the thickening about the muscular impressions, ac¬ 
companying senility. 
Fig. 13. An enlargement of the surface striae : showing the openings of the oblique tubules upon the striae 
and the scattered purictae. 
Hamilton group. Western New York. 
For further illustration, see Palaeontology of New York, Volume IV, plate vi, fig. 2. 
Orthis Vanuxemi, Hall. 
(See Plate VI a, figs. 7, 8.) 
Fig. 14. An enlargement of the surface striae. 
Fig. 15. An internal cast of the pedicle-valve ; showing the pedicle-scar and other muscular impressions. 
Hamilton group. Cumberland, Maryland. 
For further illustration, see Palaeontology of .New York, Volume IV, plate vi, fig. 3. 
Orthis Leucosia, Hall. 
(See Plate VI a, fig. 9.) 
Fig. 16. The interior of the pedicle-valve. 
Hamilton group. Western New York. 
For further illustration, see Palaeontology of New York, Volume IV, plate vii, fig. 4. 
SCHIZOPHORIA, King. 
Page 211. 
Orthis Tioga, Hall. 
Fig. 17. The exterior of a brachial valve. 
Fig. 18. An internal cast of a pedicle-valve. 
Chemung group. Near Elmira, N. Y. 
For further illustration, see Palaeontology of New York, Volume IV, plate viii, figs. 20-29. 
