39 



inches in diameter), with great accuracy, facility and 

 economy of material. No improvement is claimed for 

 the cutting disk itself. 



With this instrument can be cut sections of eight to 

 twelve square inches and from -^ to j^-q inch thick, hav- 

 ing quite true and smooth surfaces. 



2. Thin Sections and Other Specimens Illustrating 



Character of Work Done with the Dwight Pet- 

 ROTOME. Exhibited by the Department of Geology 

 and Mineralogy of Vassar College. 



The frame contains thirty-three sections of various 

 mineralogical and geological specimens of variable size, 

 all made by students of Vassar College in their regular 

 laboratory work. (This frame was exhibited at the 

 World's Columbian Exposition at Chicago.) 



Specimens on the table show various grades in the proc- 

 ess of cutting, and different methods of firmly holding 

 the object to be cut. 



3. Fossils from the Cambrian and Ordovician Rocks of 



Dutchess and Orange Counties, N. Y. 



Exhibited by Prof. William B. Dwight, Vassar 

 College, 



a. Lower Cambrian (Olenellus horizon). Camerella minor 

 and Olenellus asaphoides or O. tkompsom in quartzite 

 from Stissing Mountain, Dutchess Co., N. Y. 



b. Middle Cambrian (Olenoides horizon). Limestone from 

 Stissing Station, containing Olenoides stissingensis,, 

 Kutorgina stissingensis^ Iphidea tener. 



c. Upper Cambrian (Dikellocephalus horizon). Limestone 

 near Poughkeepsie with : Ptychoparia calcifera^ Ag- 

 raulos saratogensis, Ptychoparia spiculata^ Ltngu- 

 lep is p in n cefo rt7i is . 



d. Calciferous Limestone, Eoordovician. From Rochdale, 

 Dutchess County, N. Y. Cyrtoceras vassarina^ Or- 

 thoceras henrietta^Bathtnoceras sp. nov. nom-prop. B. 

 Americana. (The first specimen of the prosiphonata 



