14 The Naturalist in La Plata. 



is a stretch of sandy soil, or a range of dunes, there 

 it is found living ; not seen, but heard ; for all day 

 long and all night sounds its voice, resonant and 

 loud, like a succession of blows from a hammer ; as 

 if a company of gnomes were toiling far down 

 underfoot, beating on their anvils, first with strong 

 measured strokes, then with lighter and faster, and 

 with a swing and rhythm as if the little men were 

 beating in time to some rude chant unheard above 

 the surface. How came these isolated colonies of a 

 species so subterranean in habits, and requiring a 

 sandy soil to move in, so far from their proper dis- 

 trict — that sterile country from which they are 

 separated by wide, unsuitable areas ? They cannot 

 perform long overland journeys like the rat. Perhaps 

 the dunes have travelled, carrying their little cattle 

 with them. 



Greatest among the carnivores are the two cat- 

 monarchs of South America, the jaguar and puma. 

 Whatever may be their relative positions elsewhere, 

 on the pampas the puma is mightiest, being much 

 more abundant and better able to thrive than its 

 spotted rival. Versatile in its preying habits, its 

 presence on the pampa is not surprising ; but pro- 

 bably only an extreme abundance of large mammalian 

 prey, which has not existed in recent times, could 

 have tempted an animal of the river and forest- 

 loving habits of the jaguar to colonize this cold, 

 treeless, and comparatively waterless desert. There 

 are two other important cats. The grass-cat, not 

 unlike Felis catus in its robust form and dark colour, 

 but a larger, more powerful animal, inexpressibly 

 savage in disposition. The second, Felis geoffroyi, 



