EVIDENCE OF TRIASSIC INSECTS — WALKER 139 



place they now appear as raised bands 3 to 6 mm in thickness. The 

 structure of the castings in the channels is in striking contrast to 

 the normal texture and grain of the wood, which is in nearly all 

 instances at right angles to the channel. 



PALEOBUPRESTIS MINIMA, new species 

 Plate 3, B 



Type s;?6cmen.— U.S.N.M. no. 95871. 



Referred specimen. — Petrified Forest Nat. Mon. Mus. no. 183. 



Type locality. — Petrified Forest National Monument, Holbrook, 

 Ariz. 



Formation. — Triassic (Chinle) . 



Description. — These small channels measure only about 2 mm in 

 diameter. None of them can be traced more than a few centimeters. 

 It appears, however, as if some of them had completely encircled the 

 small trunk. Some of the castings were silicified and appear as 

 raised bands, while others dropped out and the work is preserved 

 only as shallow channels. The castings in the channels are in striking 

 contrast to the normal texture of the wood. 



PALEOSCOLYTUS DIVERGUS, new genus and species 



Plate 3, A 



Type specimen.— [J.^.'^M. no. 95872. 



Referred specimen. — Petrified Forest Nat. Mon. Mus. no. 184. 



Type Z(9caZ?'^2/.— Petrified Forest National Monument, Holbrook, 

 Ariz. 



Formatio n. — Triassic ( Chinle ) . 



Description. — These channels occur just under the bark. They 

 measure only about 5 mm across but are not filled with the castings. 

 The cuttings apparently fell out before being silicified. These chan- 

 nels do not as a rule go around the tree but run in all directions, and 

 consequently they appear very much like the workings of our modern 

 bark beetles or engraver beetles of the family Scolytidae. The best 

 channels of this species are found on some of the trees in the Black 

 Forest of the Painted Desert section. 



GROUP 2 



This group includes tunnels and burrows, not channels, that pene- 

 trate the heart-wood. Some occur near the bark and seem to go 

 around the log, while others seem to have bored through and through 

 the wood. The cuttings in the tunnels have been completely silicified 

 and agatized, but the tunnels are in striking contrast to the natural 

 texture of the silicified and agatized wood. In this group there are 

 two species, named as follows : 



