observed in the Gran Chaco. 221 



give a home to small mammals such as rats and mice^ and 

 the particularly beautiful and conspicuous little mouse-like 

 opossum [Marmosa pusilla). In the latter part of summer 

 the females of this opossum are frequently found almost 

 entirely concealed by their young, which cling to the 

 mother up till the time that they are nearly full-grown. 

 In the open palmar bird-life is always abundant — Icterids, 

 Finches, Woodpeckers^ and Parrots being perhaps the most 

 conspicuous of the smaller species. Occasionally a troop of 

 Rheas may be seen, which are, however, here as elsewhere 

 in the Chaco, extremely shy and difficult to approach. 

 The cry of the Chuna [Cariama cristata) is often heard, 

 especially in the early morning, while the sweet plaintive 

 call of Rhynchotiis rufescens is as characteristic a sound 

 here as it is far south on the Pampa. A conspicuous 

 mammalian inhabitant of the palmar is the Venadillo 

 {Cariacus campestris) , its larger relative the Cierbo {Cariacus 

 paludosus) being also common, but frequenting the margins 

 of the swamps. 



The islands of monte have naturally their own special 

 fauna. Of birds perhaps the most noticeable, by reason of 

 their harsh cries, are the Charata [Ortalis canicoUis) — 

 whose extraordinary voice, like the noise of an enormous 

 rattle, heard in the early morning, draws an answer from all 

 the other montes around — and Aramus scolopaceus. We 

 often detected the presence of the latter, as we stealthily 

 picked our way along the margin of the monte, by hearing 

 the continuous splashing sound just within it, the bird being 

 busily engaged in breaking the shells of the large gasteropod, 

 Ampullaria, which constitutes its favourite food in this 

 region. 



Among such surroundings, then, is situated the little 

 collection of huts called Waikthlatingmayalwa, and here 

 Mr. Budgett and I arrived at the beginning of the rainy 

 season — in October. Until the end of the year I was kept 

 busily occupied with my embryological work, but from that 

 time onwards this was rendered impossible by the greatly 

 increased depth of the swamp waters. The whole surround- 

 ing country became submerged, and we remained isolated 



