THE NA Tl 'RA L IS T. 7905 . 



ri AiE XVIII. 



Fig. 1.— Photograph of Strata at Thickley, Durham. 



a, Coal Measure Sandstone. b. Marl Slate. c, Mag-nesian Limestone. 



Fig. 2.— Teeth of Janassa bituminosa (actual size) from the Marl Slate, 

 Thickley. Durham. 



a. Crushing surface ot tooth. h. Root of tooth. c. l"nder surfaces. </. Shagreen. 



