TITK FOSSIL SLOTH AT BIG BONE CAVE, TEXX. 



67 



of quills, hairs and coprolites, the porcupine had not visited the 

 cave during the formation of Layer 3. Neither were we able to 

 find in the latter layer the wads of fine fur so characteristic of Layer 

 2 above it, but if these were specimens of sloth fur, their absence 

 is what we might have expected since the fur of the sloth could not 

 well have been scattered over a lower depth than the resting place 

 of its carcass. The absence of these ingredients, these differences 

 in character, together with its position, were sufficient to assign an 

 older date to the lower layer, whether its crusted consistency was 

 due to the infiltration of animal matter or not. According to the 

 order of formation of the different refuse, the lower layer preceded the 

 upper, and the gnawed nuts, the seeds, the fly preserving intact its 

 delicate wings, comparatively modern as they seemed, had reached 

 their position before the deposition of the bones. 



Faint from continual inhalation of the noxious dust, we had lost 

 the energy to excavate to its bottom, the last and lowest layer, 



LA YER 4, 

 {Depth unknown.) 

 a mass of fine water-laid clay, broken in lumps ranging in size from 

 six inches to a quarter of an inch in 

 diameter (see Fig. 26), covering 

 the whole floor of the gallery and 

 evidently the equivalent of the ni- 

 trous earth which had been else- 

 where removed. By their lami- 

 nated structure the lumps gave 

 evidence of their aqueous deposi- 

 tion, while hard as they now were 

 they dissolved immediately on im- 

 mersion in water. Some pieces 

 showed an irregular texture as of 

 the caking together of various par- 

 tially hardened muds, while others, 

 in the opinion of Mr. George Vaux, 

 Jr., revealed small fragments (irre- 

 ducible by boiling in water), of 

 adulterated carbonate of lime, prob- 

 ably aragonite. After digging sev- 

 eral holes in the mass to learn that 

 the manure had infiltrated downwards for at least two feet through 



Fig. 26 (actual size). — Characteris- 

 tic specimens (of Layer 4) under the 

 sloth bones. Photograph of angu- 

 lar fragments of dry cave clay, " petre 

 dirt," between which rat coprolites 

 are seen. The fragments grew larger 

 and were less mixed with manure as 

 the excavation went deeper, but the 

 bottom of this lowermost layer was 

 not reached. . 



