l8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 51 



famous as a locality for vertebrate remains. This escarpment has 

 been described by Russell, 1 Spurr, 2 and later by Collier 3 and Mad- 

 dren. 4 



The bluff region extends for a mile or more down and around an 

 almost right-angled bend in the left-hand channel of the river (see 

 fig. 2). The bluffs, from one hundred and fifty to two hundred feet 

 in height, and solidly frozen, are composed principally of an ex- 

 tremely fine silt, greenish gray in color and showing no traces of 

 stratification. Their almost perpendicular faces are being contin- 

 ually undermined (see pi. v, fig. 2) by the swift current causing 

 large masses to break off. many times with a startling report and 

 subsequent splash, as they fall into the water below. Often during 

 the two days' stay here the report sounded so like the firing of a gun 

 that we were startled by the sharpness of it. 



Xcar the lower end of these exposures the bluff's have been ele- 

 vated somewhat, exposing the gravels which underlie them. These 

 last have been called by Spurr the Palisades conglomerate, and it 

 has been suggested they may be of Pliocene age. The top of the 

 bluffs extend back from the river as a level, densely wooded table- 

 land. In several places small watercourses have dissected this 

 table, forming deep gorges. Near their mouths, where they enter 

 the Yukon, their levels are but little elevated above its high-water 

 stage. 



At the up-river end of the bluffs we found numerous bones of the 

 mammoth in the debris from a recent slide, and a short distance 

 farther down (2 on map fig. 2) the scattered elements of a bison 

 were found securely imbedded in a huge block of silt not long since 

 displaced from its original position higher in the face of the cliff. 

 The sacrum, part of the pelvis, two dorsals, rib, and scapula were 

 the parts recovered. The scapula (shoulder-blade) was quite com- 

 plete (see fig. 4), which, on account of its frail nature, appeared 

 rather remarkable, the heavier and stronger bones being broken and 

 abraded before their interment here. 



The small streams mentioned previously as dissecting the bluffs 

 were followed inland for considerable distances, and although their 

 banks in many places presented very clean-cut exposures of the silt, 

 no evidence of the presence of fossil remains was found. However, 



1 Russell, I. C. : Notes on Surface Geology of Alaska. Bull. Geol. Soc. Am., 

 vol. 1, 1890, p. 122. 



2 Spurr, J. E. : Geology of the Yukon Gold District. 18th Ann. Rept. U. S. 

 Geol. Surv., pt. 3, 1898, pp. 200-221. 



'Collier, A. J.: Bull. No. 218, U. S. Geol. Surv., 1003, pp. 18 and 43- 

 4 Maddren. A. G. : Loc. cit, pp. 17-18. 



