1894.] MAMMAI-S OP XTBUGUAT. 309 



Negro who took some interest in such things. I have since my 

 return, however, received from him the skin and skull of one. 

 The measurements of this specimen are : head and body 10 inches, 

 tail 3 inches. The fur is very soft and silky, and the hairs com- 

 posing it on the back measure from -7 to -8 inch in length. The 

 general colour of the upper parts is light hair-brown, the indi- 

 vidual hairs being tipped with this colour for -2 of their length ; 

 the basal part of each hair is mouse-colour. The chin and throat 

 are of the same brown as the rest of the head, the latter being a 

 shade darker than the back. The rest of the underparts are dirty 

 white. The tail is clothed only sparsely with bristly hairs. The 

 incisors are orange-colour, the lower ones measuring -5 inch from 

 where they emerge from the jaw-bone to their tips. It has been 

 kindly identified by Mr. Oldfield Thomas as Ctemmys brasiUetisis, 

 while a skull which I brought from a tuco-tuconale at Santa Elena, 

 Soriano, has been referred by him to Ctemmys mayellaniciis. 



Not only were the colonies where the latter specimen was found 

 smaller than those north of the Rio Negro (this might be occa- 

 sioned by the nature of the ground), but the individual burrows 

 and earths were smaller. 



From the description of some writers it might be imagined that 

 anyone being on a tuco-tuconale, whether by night or by day, 

 would hear continually the loud double or treble note from which 

 the animal takes its name. I was not so fortunate, for although 

 I have very often passed over and waited quietly about on tuco- 

 tuconales I have only once heard the sound, and that very slightly. 

 Yet the fresh workings showed that these places were inhabited. 



Eestless Cavt (Cavia apereci). 



The " Aperea," exactly hke our fancy guinea-pigs, but of a gi-ey 

 mouse-colour, paler underneath, is numerous, frequenting pajonales, 

 and, near estancia houses, strips of camp fenced in for the pro- 

 tection of young plantations. Here they make runs among the 

 grass, coming out chiefly about sundown to feed. They are almost 

 as destructive as rabbits, and where foxes (which with the Huron 

 are their chief natural enemies) have been killed down they are 

 apt to increase inconveniently. The fur is long and pretty, but 

 generally seems very loosely attached to the skin. The Aperea 

 does not burrow in the ground, though it drives tunnels in the 

 thickest pajonales ; nevertheless I have seen one, when surprised 

 on a bare river-bank, go to ground in an old ant-hole, and it is 

 probable that when the camp is very pelaclo they take refuge in 

 any convenient shelter. I have known them run into a hole in 

 the rocks and to find shelter about a shed erected for the benefit 

 of some pure-bred stock. 



Captbaba {Hydrochcerus cajpybara). 



The Capybara or Carpincho, as it is always called in Uruguay, 

 was found "^in some numbers along the Arroyo de Monzon, the 

 Arroyo Grande, and some other smaller rivers near where I was 



Peoc. Zool. Soc— 1894, No. XXI. 21 



