PLATE XXXVIII 



Okthoceras Sicinub. 



Page SOI. 



V\jl. 1. A frapm^nt showing the form and proportions of the shell, with the obscure annulations and sur- 

 face-markings. The annulations ai-e not represented sufficiently distinct. Marcelhis shale- 

 Aran. N. Y. 



Kip. 2. An enlargf-ment of the surface of the preceding specimen, showing' the rounded annulation.s and 

 reticulate surface. 



OrTHOCERAS 8UBTJLATUM. 



Page 283. 



See Plates 84, 86. 



Fip. 3. The original of the species, which is nearly entii-e, preserving the chamber of habitation. The 



specimen is flattened fi-om pressure in the shale. Marcellus shale. Bloomfield, N. Y. 



Okthoceras Marcellense. 



Page 278. 



See Plate 83. 113. 



Fig. 4. A fragment preserving several of the air-chambers, and a portion of the test with the external 



markings. 

 Fig. 5. Tlie ventral side of a larger fragment retaining portions of the test over the surface, and the carina 



on the internal mould, which is too prominently represented along the chamber of habitation 



t<iwards the aperture. ~ 



Fig. 6. A nearly entire individual showing the length of the outer chamber and the increase in the frequency 



of the septa toward the apex. The peculiar organic deposit and ornamentation of the internal 



cast, shown in the specimen, are not represented in the figui-e. The apex is i-epresented as 



entire, but several air-chambei-s are wan'ing in the specimen. 

 Fig. 7. A larger example, imperfect at both extremities, retaining fragments of the test on different parts of 



the surface. 

 Fig. 9. An enlargement of the surface, showing the transverse strise interrupted by longitudinal lines. 



The above specimens are all from the Gouiatite limestone of the Marcellus shale. Manlvim, 



Marcellus, and other places in New York. 



Orthoceras APTUM. 



Page 2S2. 

 Fig S An individual presei-ving the greater portion of the chamber of habitation, and over thirty air- 

 chamt)er8, showing the gradually enlarging tube, and the curved and oblique septal sutures : 

 doi-sal view. Goniatite limestone. Manlius, N. Y. 



Orthoceras Bebrtx. 



Page 275. 

 See Plates 39, £3, 84. 

 Fig. 10. A large fragment of the septate porlion, retaining a part of the chamber of habitation. Hamilton 

 shales. Caienovia, N. Y. ' 



