MAMMALIA. 
79 
to the Rio Chupat in 43° 20'; — distance of 1160 miles. This latter river is 170 
miles south of the Rio Negro, and the intervening space consists of level, ex- 
tremely arid, and almost desert plains, with no water, or at most one or two small 
wells. As the Coypu is supposed never to leave the banks of the rivers, and 
being, from its web-feet and general form of body, badly adapted for travelling- 
on land, its occurrence in this river is a case, like so many others in the geogra- 
phical distribution of animals, of very difficult explanation. The same remark is 
indeed applicable, but with less force, to its existence in the Rio Negro. On the 
west coast, it is found from the valleys of central Chile (Lat. 33°) to 48° S., or 
perhaps even somewhat farther, but not in Tierra del Fuego. So that, on the 
Atlantic side of the continent, the plains of Patagonia check its range south- 
ward, as, on the Pacific side, the deserts of Chile do to the north. Its range, in- 
cluding both sides, is from 24° to 48°, or 1440 miles. In the Chonos Archipelago 
these animals, instead of inhabiting fresh water, live exclusively in the bays and 
channels which extend between the innumerable small islets of that group. They 
make their burrows within the forest, a little way above the rocky beaches. I 
believe it is far from being a common occurrence, that the same species of any 
animal should haunt indifferently fresh water, and that of the open sea. We shall 
see that the Capybara is sometimes found on the islands near the mouth of the 
Plata ; but these cannot be considered as their habitual station in the same 
manner as the channels in the Chonos Archipelago are to the Coypu. The in- 
habitants of Chiloe, who sometimes visit this Archipelago for the purpose of fish- 
ing, state that these animals do not live solely on vegetable matter, as is the case 
with those inhabiting rivers, but that they sometimes eat shell-fish. The Coypu is 
said to be a bold animal, and to fight fiercely with the dogs employed in chasing 
it. Its flesh when cooked is white and good to eat. An old female procured 
(January) amongst these islands, weighed between ten and eleven pounds.” D 
Family — OCTODONTIDiE. 
Ctenomys Braziliensis. 
Ctenomys Braziliensis, De Blainville , Bulletin de la Societe Philomatique, June 1836, p. 62. 
Maldonado, La Plata, {June.) 
“ This animal is known by the name of Tucutuco. I have given an account of 
its habits in my journal, but I shall here repeat it for the sake of keeping 
