PLATE LXXXVIII. 



Obthogeras Atreus. 



Page 30E. 

 See Plate 89. 

 Vig. 1. A portion of an individnal, preserving a large part of the chamber of habitation and nine air-cham- 

 bers, showing the cylindrical chamber of habitation, with its constriction and the conti-action ot 

 the tube at the aperture. The specimen is considerably compi'essed. Several branching, 

 tubular furrows of a teftbrous animal are shown traversing portions of the tube. Portage 

 gi-oup. Rogers' Bridge, on the Oenesee River below Portageville, iV. T. 



Orthoceras Thtestes. 



Page 306. 

 Fig. 3. A much compressed and broken specimen, showing a portion of the chamber of habitation and 

 twenty-foiir attached air-chambers. The comparative depth of the air-chambers in this 

 species and O. Atrefiia, and the more rapid enlargement of the tube, is clearly shown in the 

 figures. Several Cranue are attached to the chamber of habitation The ventral valves of 

 two individuals ai"e shown as merely a thickened rim. Three doi-sal valves are repiesented, 

 showing a subcentral apex, and concentric lamellose lines of growth. This species is here 

 designated as Omnia centnUit. 



