140 PROCEEDINGS OF THE ]S^ATIO:^;AL MUSEUM vol.85 



PALEOIPIDUS PERFORATUS, new genus and species 



Plate 4, B 



Tyfe spechnen. — U.S.N.M. no. 95873. 



Referred specimen. — Petrified Forest Nat. Mon. Mus. no. 185. 



Type JocaUty. — Petrified Forest National Monument, Holbrook 

 Ariz. 



Formation. — Triassic (Chinle) . 



Description. — These tunnels seem to go through and through the 

 wood. They measure about 5 mm in diameter but appear to be 

 angular rather than round. In some cases they are exposed by 

 decay or weathering of the wood, and they appear square to rec- 

 tangular in outline. Cross sections Viewed in the solid matrix appear 

 oval in outline but with a flattened surface on one side ; the silicified 

 cuttings are in striking contrast to the normal texture of the wood. 



PALEOIPIDUS MARGINATUS, new species 



Plate 4, A 



Type specimen. — U.S.N.M. no. 95874. 



Referred specimen. — Petrified Forest Nat. Mon. Mus. no. 102. 



7'ype locality. — Petrified Forest National Monument, Holbrook, 

 Ariz. 



Formation. — Triassic (Chinle) , 



Description. — These tunnels that occur in the heart-wood may be 

 observed only in a few polished sections on exhibit in the museum. 

 Tunnels of two sizes are recognized, one measuring about 2 mm, the 

 other 3 mm, in diameter. In the few complete log sections where 

 these tunnels have been observed, they never penetrate more than 

 10 or 20 cm from the margin or probable bark layer. The castings 

 have been completely agatized but may be easily traced across a 

 polished surface. 



SUMMARY 



As far as I have been able to observe, the only species of tree at- 

 tacked by the borers is Araucarioxylon arizonicum. In no instance 

 has there been found evidence of insect activity in either Wood- 

 (worthia or Bchilderia^ the other two known genera of fossil trees from 

 the Petrified Forest National Monument area. 



The large channels of Group 1 resemble somewhat the work of some 

 modern buprestids, and it seems logical to believe that many of the 

 trees were girdled and killed. In that way one might account for 

 such a concentration of logs as occurs at about the 300-foot level in 

 the Chinle of this region, where it is estimated that approximately 

 50 percent of the log sections show evidence of being attacked 

 by these borers. 



