PLATE CXIII. 
Bactrites clavus. 
Page 316. 
See Plate 84. 
Fig-. 1. Ventral (?) view of an individual, preserving a portion of the chamber of habitation and twenty-five 
air-chambers, showing the form of the shell, the “ dorsal lobe ” and the curvature of the sutures. 
The greater portion of the shell has been filled and replaced by iron pyrites, which has formed 
an irregular mass at the upper extremity of the chamber of habitation. The apical air- 
chambers have not been filled with this mineral, and are macerated and disturbed by com¬ 
pression. Marcellus shale. Schoharie , N. Y. 
Fig. 2 id. An enlargement of five air-chambers, showing the different aspects of the “ dorsal lobe,” as pro¬ 
duced by the exfoliation of the test. In no case is it a sinus in the septal margins, but is a 
hiatus in the walls of the internal mould of the air-chambers, from the contact of the siphun- 
cular tube with the inner surface of the test. 
Fig. 3 id. Lateral view of three air-chambers, showing the curvature of the sutures over the lateral face of 
the tube, and the concavity of the septa in a dorso-ventral direction. The tube of the siphuncle 
is slightly projecting from the lower septum, and the septa are somewhat advanced on this side. 
Frg. 4 id Dorsal view of the same, showing the slight longitudinal carina along the walls of the air-chambers 
and the concavity of the septa in a lateral direction. 
Fig. 5 id. A septum showing the transverse section of the tube, and the size and position of the siphuncle. 
Orthoceras scintilla. 
Page 293. 
See Plate 84. 
Fig. 6. A specimen, natural size, showing the form of the shell and the depth of the air-chambers. From 
the shales of the Hamilton group. Pratt's Falls, Onondaga county, N. Y. 
Fig. 7. An enlargement of a longitudinal section of three air-chambers, showing the concavity of the septa 
and the large central siphuncle, without any expansions of its tube or circumposed organic 
deposit. 
Fig. 8. A similar enlargement of another fragment, showing the expansion of the siphuncular tube, princi¬ 
pally at one side. 
Fig. 9. Another fragment in which the siphuncle is equally expanded in the anterior portion of each air- 
chamber. 
Fig. 10. An enlargement of the lower septum of fig. 7, showing a small concentric areola around the insertion 
of the siphuncle. 
Fig. 11. A septum corresponding to fig. 8, showing the central position of the siphuncle at its insertion in 
the septum, and the excentric areola from the asymmetrical expansion of the tube in the cavity 
of the preceding air-chamber. 
Fig. 12. A septum of specimen fig. 9, with a large central areola around the insertion of the siphuncle, 
corresponding to the great expansion of the tube in the air-chambers. 
Orthoceras crotalum. 
Tage 296. 
See Plates 42, 82. 
Fig. 13. The apical portion of a small individual enlarged three diameters, preserving the initial extremity, 
and showing the umbilical cicatrice at the apex, the ornamentation of the test, and the depth 
of the air-chambers. The first air-chamber is seen to be much deeper than those succeeding. 
Hamilton group. Pratt's Falls, N. Y. 
Fig. 13 a. The initial extremity of the preceding, further enlarged, to show the characters of the umbilical 
cicatrice more in detail. 
