PLATE CXIII. 



Bactritbs clavds. 



See Plate 84. 



fig. 1. Ventml(1) view of an individual, pi-esei-ving a portion of the chamber of habitation and twenty-five 

 air-cbaiiibei-s, showing the form of the shell, the " dorsal lobe " and the cui'vature of the sutures. 

 'ITie greater iK)rtiou of the shell has been tilled and replaced by iron pyrites, which has formed 

 an irregular mass at the upper exti-emity of the chamber of habitation. The apical air- 

 chambere have not been filled with this mineral, and are macerated and disturbed by com- 

 pression. Marcellus shale. Schoharie, N. Y. 



Vig. 3 id. An enlargement of five air-charabei-s, showing the different aspects of the " doi-sal 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-chambei's, fi'om the contact of the siphun- 

 calar tube with the inner surface of the test. 



Pig. 8 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 dii-ection. The tube of the siphuncle 

 is slightly pi-ojecting from the lower septum, nnd the septa are somewhat advanced on this side. 



Kig. 4 id Doi-sal view of the same, showing the slight longitudinal carina along the walls of the air-chambei-8 

 and the concavity of the septa in a latei-al direction. 



Pig. iid. k septum showing the transverse section of the tube, and the size and iwsition of the siphuncle. 



Orthockras scintilla. 



Page 293. 

 See Plate 84. 



Pig. 6. A specimen, natural size, showing the form of the shell and the depth of the air-chambei-s. Prom 

 the shales of the Haipilton group. JPratt's Palls, Onondaga county, iV. T. 



Pig. 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 cii-cumposed organic 

 deposit. 



Tig. 8. A similar enlargement of another fragment, showing the expansion of the siphnncular 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. H. A septum con-esponding 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-chaml>er. 



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-chambei-s. 



Orthoceras crotalum. 



Page 296. 

 See Plates 42, 82. 

 Vig. 13. The apical portion of a small individual enlai'ged three diameteiv, preserving the initial extremity, 

 and showing the umbilical cicatrice at the apex, the oi-nanientation of the test, and the depth 

 of the air-chambei's. 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 charactera of the umbilical 

 cicatrice more in detail. 



