PLATE IVf—C ontinued. 
Orbiculoidea Newberryi, Hall. 
18. The same features; showing the strong elevation of the area, but the absence of callosities, the 
large foramen, the, sharply defined, though flattened median ridge and lateral walls of the 
pedicle-passage. X 3. 
Waverly group. Cuyahoga Falls, Ohio. 
(From the original locality, a, ferruginous band about 110 feet below the conglomerate.) 
(EHLERTELLA s.-gen nov. 
Page 120. 1 . : . 
CEhlertella pleurites, Meek. 
19. The internal characters of the pedicle-area; showing the open marginal; foramen, the elevated, 
radially striated lateral walls, the median ridge and a short apical septum. X 3. 
20. The same features from a iOther specimen, in which the walls of the area are smooth and the apical 
septum absent. X 3. 
Waverly group. Newark, Ohio. 
ORBICULOIDEA, D’Orbigny. 
Page 120. " M l 
Orbiculoidea Lodensis, Vanuxem. 
21. The internal characters of the pedicle-area; indicating the unusual breadth and depth of the base 
of the groove and the low lateral walls ; also the interruption in the ornamention of the shell 
from the foramen outwards, probably indicating the line of union of the primitive 1 margins of 
the aperture:' X 4. 
Genesee shale. Lodi, N. Y. 
Orbiculoidea, sp, indet, « 
ll 22. A natural cast of the interior apical portion of the brachial valve ; showing the anteifipr and pos¬ 
terior muscular ridges. X 3 
Chemung group. Warren, Pa. 
Orbiculoidea nitida, Phillips. 
23. The pedicle-area of an extremely young shell, having a diameter of 1 mm. The foramen is a 
marginal slit extending, with divergent edges, for almost the entire radius of the valve. At 
the apex, the pedicle-groove appears in an incipient stage. X 50. 
24. A considerably later stage of development of these parts, the diameter of the shell being 5 mm. ; 
showing the margins of the foramen united for most of their length, but still separated at the 
posterior edge of the valve. The, structure of the area is somewhat obscured by the compres¬ 
sion of the specimen. X 12. 
25. A later stage of growth; exhibited by a specimen 7 mm. in diameter. Here the angles 'made by 
• the edges of the foramen with the posterior edge of the shell are [acute and approximate. The 
pedicle-groove has progressed so as nearly to fill the entire hiatus. X 7 
Figures,23-25 are from a block of black shale,upon which valves of this species are crowded in 
great numbers, to Ike.(exclusion, of other fossils. The condition of the pedicle-area in its later 
development, as shown in the following figures, is also, amply represented in these specimens..; 
Lower Coal Measures. Springfield, Illinois. 
'26. The internal pedicle-area of a small but mature individual;..showing the base and lateral walls 
of the groove and the slight callosity at the apical extremity. X 7. 
27. The external surface of a similar specimen ; showing the,general form , of the groove at maturity, 
and the absence of any furrow or interruption of the concentric ornamentation beyond its pos¬ 
terior extremity. X 7. 
28. The entire valve, of which fig. 27 represents the pedicle-area. X 2. 
Coal Measures. Grrover, Missouri. 
29. The interior of a pedicle-valve; showing the base of the groove, the foramen and the muscular 
impressions. (After Davidson. Brit. Carb. Brach., Suppl., pi. xxx, fig. 13 a.) 
Orbiculoidea, sp.. Meek. 1 
31. “ An impression of the outside of the under valve in the matrix (slightly less than natural size), 
with portions of the thin shell adhering, so as to show the smooth inside, and a prominent 
internal ridge, corresponding to a deep external furrow, with a small, round, or oval foramen 
at its outer end.” (Meek, Palsetolugy of Eastern Nebraska, plate iv, fig. 3, and Explanation.) 
Coal Measures. Near Nebraska CUy,,$efc. , \ 
