PROCEEDINGS OF THE ACADEMY OF [July, 



latter remains as the most probable climatic condition of the Triassic 

 period in Eastern North America. 



Explanation of Plates III, IV. 



Plate III. — Fig. 1. — Araucarioxylon virginianum Knowlton. Locality B. 5. 

 Transverse section, X 20. No definite annual ring. 



Fig. 2. — .Same. Radial section, X 40. Shows several double rows of pits. 



Fig. 3. — Same. Tangential section, X 40. Shows cross-section of medul- 

 lary rays and of radial wall pits. 



Fig. 4. — Araucarioxylon vanartsdaleni sp. nov. Locality B. 5. Transverse 

 section, X 20. No annual ring. 



Fig. 5. — Same. Radial section, X 40. Shows one of the very rare double 

 rows of pits. 



Fig. 6. — Same. Tangential section, X 40. Shows few-celled rays. 



Plate IV. — Fig. 1. — Brachyoxylon -pennsrjlvanianum sp. nov. Locality C. 1. 

 Transverse section, X 20. Shows distinct annual ring of four layers of 

 small cells just above middle. 



Fig. 2. — Same. Radial section, X 40. Shows single rows of pits, dis- 

 tinctly separated. 



Fig. 3. — Same. Tangential section, X 40. Shows medullary rays. 



Fig. 4. — Same. Another radial section, X 40. Shows several double rows 

 of pits, which are only partially alternate. 



Fig. 5. — Same as figure 4, but X 100. 



Fig. 6. — The section shown in Plate III, fig. 3, under crossed nicols (X 40), 

 showing the complete replacement by crystalline quartz. 



