1912.] NATURAL SCIENCES OF PHILADELPHIA. 369 



walled, moderately large (about 0.04 mm. in diameter) in radial 

 rows. 



Radial Section: Tracheids long, thick walled; bordered pits 

 in one or frequently two series; wdien in one, in contact and flattened; 

 in two, closely packed, alternate, strongly hexagonal, and nearly 

 covering the walls of the cells (diam. 0.016 to 0.021 mm.); medul- 

 lary rays long, without pits; resin ducts none. 



Tangential Section: Rays simple, of 1 to 27, usually 10-12 

 cells about 0.025 mm. in diameter; no pits on walls, but cross- 

 sections of radial wall pits prominent. 



Occurrence: This species, hitherto found near the base of the 

 Triassic in North Carolina, Virginia, and Connecticut, is now re- 

 ported for the first time from Pennsylvania, being occasionally found 

 at localities B. 2 and B. 5. 



Relationship: Araucarioxylon (Dadoxylon) rhodeanum Goppert, 

 from the Permian of Silesia, appears from descriptions to be very 

 similar to this species, but distinctive features would no doubt be 

 found if well-preserved specimens could be compared. 



Araucarioxylon vanartsdaleni ap. nov. Plate III, figs. 3-6. 



Transverse Section : Annual ring indistinct ; tracheids averag- 

 ing 0.03 mm. in diameter, thick walled. 



Radial Section: Tracheids long, thick walled, with bordered 

 pits (diam. 0.015-0.020 mm.) usually in single rows, barely touching, 

 and but little compressed; about one cell in every fifty with double 

 rows, which are alternate and hexagonal; medullary rays long 

 (at least, no partitions preserved), without pits; resin ducts absent. 



Tangential Section: Ray cells rather small (diam. 0.02 mm.), 

 up to 10 in one row, though usually 5 or 6; pits absent. 



Occurrence: This appears to be the most widespread form in 

 the Triassic of Pennsylvania, occurring at practically every locality 

 on the list. 



Relationship: When first examined all of the wood with con- 

 tiguous pits was referred to A . virginianum, but the study of a large 

 number of specimens indicates that there are probably two distinct 

 species represented, and the one characterized here differs from 

 A. virginianum as well as from A. woodworthi Knowlton, which 

 occurs near the top of the Triassic in Virginia, in the fewer-celled 

 medullary rays and the predominance of the uniserial arrangement 

 of the pits. It is therefore regarded as new, and named after its 

 discoverer. Its nearest relative in other regions is A. wurtemburg- 



