Fossils of the TJtica Slate. 



19 



Formation and locality, Utica slate, town of Trenton, Oneida 

 Co., N. Y. 



Ctathophycus subsphericus n, sp. 

 Plate II, figure 17. 



Hollow membraneous fronds with a circular opening at the apex 

 of a nearly hemispheric body. 



This species is less firm in structure than the proceeding, there 

 being no thickening of the cell walls to give the reticulated appear- 

 rance and to preserve the form, which varies from circular to 

 oval as if a hemispheric body had been pressed flat. In an example 

 three centimetres in diameter, the circular opening is nine milli- 

 metres in diameter. 



Forfnation and locality, Utica slate, town of Trenton, Oneida 

 Co., N. Y. 



DISCOPHYCUS nov.gen. 



Ai(fxog — a disk ; ^\>xog — a sea weed.. 

 Discoid, slightly convex fronds ; circular or orbicular in outline 

 substance coriaceous. 



DiSCOPHYCUS TTPICALIS W. Sp. 



Plate II, figures 18, 18a. 



Frond discoid, more or less convex owing to degree of compres- 

 sion. Outline clearly defined, varies from circular to orbicular when 

 unbroken before being imbedded in the sediment, assumes various 

 shapes when broken and pressed out. The substance appears to have 

 been of a coriaceous nature as it is slightly corrugated on the outer 

 margin in some fronds, and frequently shells of the genera Orthis 

 and Pterinea are attached to it, forming small colonies upon 

 the smooth, dark lustrous surface. In several large entire, and 

 also fragmentary, specimens the outer margin appears as though a 

 gelatinous or carnose body had been pressed flat between the layers 

 of shale. 



Fronds vary in size from four to twelve centimetres in diameter. 



Formation and locality, Utica slate, town of Trenton, Oneida 

 Co., N. Y. 



