72 



a finely and irregularly corrugated surface ; this is no doubt a faint 

 reflection of the original structure of the wood as seen in transverse 

 section. 



51.622. Dark transverse section of jet. Of. 51,623 (Eig. 7, 

 PI. VIII.). 



51,782. A small piece of a longitudiaal section of jet showing 

 numerous fine dark lines indicating the walls of the tracheids. 



51,806. Prohahly a longitudinal tangential section ; the matrix 

 is traversed by wavy dark bands of unequal thickness. 



52.623. Specimens of fossil wood and jet. 



