PLATE LXXXVII. 



Orthoceras Eriense. 



Page 274. 

 See Plate 40. 

 Figf. 1. The chamber of habitation of an individual referred to this species. The specimen is somewhat 

 broken fi-om compression, and the test has been replaced and the surface-markings obliterated 

 by iron pyrites. 

 Fig. 2. A septum from the preceding specimen, showing the position of the siphuncle and the amount of 

 compression. 



Othoceras lintecm. 



Page 277. 

 Pig. 3. A fi-agment, preserving a portion of the chamber of habitation, with the last air-chamber, showing 



the surface-raarldngs over the entire tube. Leonardsville, Madison county, N. T. 

 Fig. 4. A portion of the surface enlarged four diameters to show the character of the striae. ^ 



Orthoceras, sp. undetermined. 



Figs. 5, 6. Two figures representing a not uncommon condition of preservation of the fossils in the softer 

 shales. The shell has evidently been macerated, and surrounded by a concretionary mass of 

 of the clay forming the shale — the whole being subjected to compression. From the effects of 



' compression, and the mode of accretion, the specimens are often regularly striated, as repre- 



sented in these figures ; and in two specimens of 0. subulatum, illustrated on plate 84, exhibit  

 the same conditions in the anterior air-chambers : giving the appearance termed " slickensides." 

 The specimen, figure 5, is from the soft shales at Pratts Falls, Onondaga county, N. Y., 

 and the larger one is found in a similar situation at Eighteen-mUe Cfreek, on Lake Erie Shore, 

 near Buffalo, N. T. 



