Foerste.] 
354 
May 1, 
valve, and a line indicating its lack of convexity ; fig. 27, ventral valve, 
with a line indicating its convexity. C. T. 
Mg. 29. Stricklanclinia lens, Sowerby? ventral valve and a ling, indicat- 
ing its convexity. C. T. 
Fig. 30. Ptilodictya emarcescens, Foerste. Fig. 30a, part of a frond, 
with a section showing its convexity; fig. 306, a part of the same magni- 
fied. E. O. 
Fig. 31. Ptilodictya farctus , Foerste. Fig. 31a, part of a frond, with a 
section showing its convexity; fig. 316, a part of the same enlarged. E. 0. 
Fig. 32. Ptilodictya famelicus, Foerste. Fig. 32a, parts of two fronds 
with section showing their convexity; fig. 326, a part of the left hand 
specimen enlarged. E. 0. 
Fig. 33. Ptilodictya metis , Foerste. Fig. 33a, parts of two fronds with 
sections showing their convexity; fig. 336, a part of the left hand spec- 
imen enlarged. 
PLATE VII. 
Figs. 1, 2. Orthoceras rectum, Worthen, var. junior. Fig. 2, a side view; 
fig. 1, a specimen with a smooth exterior, perhaps of this species. H. I. 
Fig. 3. Orthoceras Jamesi, Hall and Whitfield. Side view. Todd’s 
Fork, Ohio. 
Fig. 4. Orthoceras ignotum , Foerste. A vertical section through the 
siphon, with a transverse section indicating the position of the same. H. I. 
Fig. 5. Orthoceras virgulatum, Hall? A vertical section through the 
siphon. S. O. 
Fig. 6. Orthoceras Hanoverensis, Foerste. The upper part of the figure 
i^fig. 6a) represents a view of the cast of the interior of the shell; the 
lower part represents a vertical section of the same passing through the 
siphon ; fig. 66 represents a part of the other side of fig. 6a, where it has 
been weather-worn. H. I. i 
Fig. 7. Cyrtoceras ? subcompressum, Hall. Fig. 7a is a side view of two 
fragments upon which this species is founded ; the smaller, the type ; the 
larger, a part of the living chamber, placed in the position they are sup- 
posed to have once occupied, while the character of the remainder of 
the coil is conjecturally indicated. The diameter of the whole is reduced 
to one-fourth. The coil as here figured is imaginary. It may have been 
a closed coil but probably was not; fig. 76, a vertical section through the 
type showing the character of the siphon; fig. 7c, a transverse section of 
the living chamber near the last septum reduced to one-half the diameter ; 
fig. 7 d, showing the character of the surface marking of the type at d, in 
fig. 7a, but representing them far more distinctly than warranted by their 
actual state of preservation. B. 0. 
Fig. 8. Cornulites serpularius var. Clintoni, Hall. C. A. 
PLATE VIII. 
Fig. 1. Orthoceras Nova- Carlislensis, Foerste. View of interior cast. 
B. 0. 
