PLATE LVIII. 
G-yroceras Eryx. 
Page 386. 
See Plate 103. 
Fig-. 1. A septate fragment of this species, showing the curvature of the tube and the depth of the air- 
chambers. From Dolomitic limestone, referred to the Hamilton group, near Milwaukee, Wis. 
Trochoceras Orion. 
Page 397. / 
Fig. 2. Lateral view of a fragment, showing the curvature of the tube, the gibbous chamber of habitation 
becoming straight, and contracting near the aperture. The sinus represented on the dorsal 
side of the aperture is incorrect, and is not shown on the specimen. A broad sinus in the 
ventral margin corresponds to the sinus of the surface-markings on the convex side of the tube. 
Schoharie grit. Eelderberg mountains, N. Y. 
Trochoceras eugenium. 
Page 396. 
See Plate 59. 
Lateral view of a small, compressed specimen, showing the curvature of the tube and the depth of 
the air-chambers. Schoharie grit. /Schoharie, N. Y. 
A small, compressed, septate fragment, referred to this species with doubt. The air-chambers are 
shallower than is usual in the species, and it may belong to the apical portion of G-yroceras 
spinosum, but does not preserve any remains of the revolving rows of spines. The obliquity 
of the septa and the slight deflection of the tube may be due to compression. 
Trochoceras obliquatum. 
Page 401. 
See Plate 111. 
Fig. 5. The concave dorsal side of a specimen, showing the transverse'section of the tube and the want 
of symmetry in the curvature. The view is looking upon the specimen obliquely, which 
somewhat exaggerates the departure of the curvature from one plane. Schoharie grit. /Scho¬ 
harie, N. Y. 
Trochoceras expansum. 
Page 402. 
See Plate 111. 
Fig. 6. The concave dorsal side of a compressed septate fragment, showing the depth of the air-chambers, 
the curvature of the sutures, and the slight departure of the volution from one plane. Scho¬ 
harie grit. Schoharie, N. Y. 
Trochoceras Pandion. 
Page 400. 
See Plate 111. 
Fig. 7. Lateral view of a fragment, showing the angular form of the tube, the depth of the air-chambers, 
and the obliquity of the septa. Traces of the siphuncle are seen-on the convex ventral side as 
exposed in the process of weathering. Schoharie grit. Schoharie, N- Y. 
Fig. 8. Lateral view of a specimen preserving about one volution, showing the curvature, and form of the 
shell. The apical portion is much compressed, and the evidences of the air-chambers oblit¬ 
erated. Schoharie grit. Schoharie, N. Y. 
Fig. 9. A septum of a fragment, showing the transverse section of the tube and the position of the siphun¬ 
cle. Schoharie grit. Schoharie, N. Y. 
Fig. 3. 
Fig. 4. 
