PLATE XLVII. 
Cyetooekas (G-omphoceras) metula. 
Page 360. 
See Plate 111. 
Fig. 1. Ventral view of a chambered fragment, showing the enlargement of the tube and the depth of the 
air-chambers. 
Fig. 2. Lateral view of the preceding, showing the amount of the curvature of the tube. Upper Helderberg 
limestone. Clarence Hollow, N. Y. 
Cyrtoceras morsem. 
Page 367. 
Fig. 3. Ventral view of a fragment which is imperfect at the apex, showing traces of the transverse costae 
of the test and the slight sinus along the ventrum. 
Fig. 4. Lateral view of the preceding, showing the curvature of the tube. This specimen is the type of the 
species, and is from the Upper Helderberg limestone. Clarence Hollow, N. Y. 
Cyrtoceras eugenium. 
Page 369. 
See Plates 36, 96, 97. 
Lateral view of an individual nearly entire, showing the straight outer portion and curved apex. 
Several fragments of the test, preserving the surface-markings and ornaments, are adhering to 
parts of the tube. The internal mould preserves the furrows of the crenulations and the annu- 
lations marking the exterior ridges of the test. 
Ventral view showing the sinus of the ornaments and aperture, with the variation in the prominence 
and frequency of the annulations aud transverse ridges toward the apex and near the aperture. 
Dorsal view of the straight portion of a large individual showing a slight gibbosity, due to the 
gradual contraction of the tube toward the aperture. The dorsal margin of the aperture is 
shown to be continuous and entire. In this example the prominent expansions of the test 
become obsolescent toward the aperture, where the shell is marked by lamellose lines of growth. 
These specimens are from the Upper Helderberg limestone, at Schoharie, N. Y. 
GYROCERAS spinosum. 
Page 382. 
See Plates 48, 49, 98, 99. 
Fig. 8. Ventral view of a compressed specimen, showing the nummuloid elements of the siphuncle, as exposed 
in the process of weathering. Schoharie grit. Schoharie, N. Y. 
Fig. 5. 
Fig. 6. 
Fig.J. 
