30 LAND MAMMALS IN THE WESTERN HEMISPHERE 



tances of hundreds of miles. Thus will be buried the scattered 

 bones, skeletons, carcasses, that happen to be lying on the sur- 

 face ; and if the fine fragments are falling rapidly, many animals 

 will be buried alive and their skeletons preserved intact. A 

 modern instance of this is given by the numerous skeletons of 

 men and domestic animals buried in the volcanic ash which 

 overwhelmed Pompeii in 79 a.d. Pliny the Younger, who 

 witnessed that first recorded eruption of Vesuvius, tells us in 

 a letter written to Tacitus, that far away at Misenum, west of 

 Naples, it was often necessary to rise and shake off the falling 

 ashes, for fear of being buried in them. In the Santa Cruz 

 formation of Patagonia (see p. 124), which has yielded such a 

 wonderful number and variety of well-preserved fossils, the 

 bones are all found in volcanic dust and ash compacted into 

 a rock, which is usually quite soft, but may become locally 

 very hard. The Bridger formation of Wyoming (p. 110) and 

 the John Day of eastern Oregon (p. 116) are principally made 

 up of volcanic deposits ; and no doubt there are several others 

 among the Tertiary stages which were formed in the same 

 way, but have not yet received the microscopic study necessary 

 to determine this. 



Much information concerning the mammalian life of the 

 Pleistocene, more especially in Europe and in Brazil (p. 211), 

 has been derived from the exploration of caverns. Some of 

 these caves were the dens of carnivorous beasts and contain 

 multitudes of the bones of their victims, as well as those of 

 the destroyers themselves. Others, such as the Port Ken- 

 nedy Cave, on the Schuylkill River above Philadelphia, the 

 Frankstown Cave in central Pennsylvania, the Conard Fissure 

 in Arkansas, are hardly caverns in the ordinary sense of the 

 word, but rather narrow fissures, into which bones and car- 

 casses were washed by floods, or living animals fell from above 

 and died without being able to escape. The bones are mostly 

 buried in the earth which partially or completely fills many 

 caverns and may be covered by a layer of stalagmite, derived 



