PLATE LX XXI. 
Orthoceras prayum. 
' Page 255. 
See Plates 35, 36, 112. 
Fig..l. An individual, preserving the base of the chamber of habitation and eight adjacent chambers. The 
specimen is much flattened and distorted from compression; the chambers have become par¬ 
tially separated along one side, and'their normal form much modified. Clarksville, N. Y. 
Fig. 2. A septate fragment, showing the regularity in the depth of the chambers and the gradual enlarge-. 
ment of the tube. The lower portion has been flattened, producing a longitudinal furrow, as 
represented in the figure, probably from the infolding and subsequent erosion of the shell. 
The ornamentation on the margins of the septa and on the chamber walls is not shown in the 
figure. 
Fig. 3. A small fragment of five chambers, showing the concave and convex chamber walls, as produced by 
compression. Schoharie, N. Y. 
Fig. 4. A longitudinal section of three of the chambers of the preceding specimen, showing the indentations 
in the septa made by tne siph uncle. No traces of the siphuncle, in its passage through the 
chambers, can be observed. The figure does not quite correctly represent the depth of the 
chambers, and is not complete above. 
Fig. 5. Ventral view of two chambers from the upper portion of the specimen figure 2, showing the exten¬ 
sion of the areola to the margin of the septa, and its surrounding with concentric strife. 
Fig. 6. The apical portion of an individual, presenting the appearance of a gradual absorption and final 
truncation of the shell. The siphuncle has become exposed from the process of weathering. 
Sharp longitudinal striae, partially represented, but shown over several chambers, are prob¬ 
ably the remains of the ornamentation or vascular markings on the septa. Schoharie, IV. Y. 
Fig. 7. A septum, showing the areola and its strife surrounding the siphuncle and extending to the ventral 
margin. 
Fig. 8. Another example, similar to the preceding, somewhat enlarged. 
Orthoceras oppletum. 
Page 248. 
See Plate 112. 
Fig. 9. Ventral view of a fragment, showing the lamellose striae on the chambers and septa, and the cylin¬ 
drical aggregation of the organic deposit around the siphuncle. Schoharie, N. Y. 
Fig. 10. Lateral view of the preceding specimen. The striae are seen to be concentric about a point on one 
of the septa. 
Fig. 11. A septum of the preceding specimen, showing the size and position of- the siphuncle. 
Fi<r. 12. A fragment, with the cavities of the chambers nearly filled with an organic deposit. Schoharie, N. Y. 
Orthoceras luxum. 
Page 244. 
See Plates 35, 76, 77, 78, 78 B, 112. 
Fig. 13. A septate fragment, with the exterior walls of the chambers removed, leaving the cylinder of 
organic deposit surrounding the siphuncle. The septa are closer together, and the furrows on 
the cylinder are smaller than in the preceding species. 
