No\T!MBER 1, 1894.] 



KNOWLEDGE. 



243 



under the floors of out-buildings, whence they issue forth 

 to feed at night. All the true cavies are small and short- 

 legged creatures ; but the Patagonian cavy, representing 

 the genus Dolichotis, is a much larger and taller animal, 

 measuring nearly a yard in length, and standing over a 

 foot at the shoulder. An inhabitant of the open districts 

 of Patagonia and Argentina, the mara, as it is called by 

 the natives, much resembles a hare in its movements. 

 Unfortunately, the spread of cultivation has well-nigh 

 exterminated this handsome rodent from most parts of the 

 Argentine. Largest, not only among South American 

 rodents, but likewise in the entire order, is the aquatic 

 carpincho or capivara {ILjdrochi'rus), attaining a length of 

 upwards of four feet. The most remarkable peculiarity of 

 this animal is the large size and complex structure of the 

 last molar tooth, which in the upper jaw may have as 

 many as twelve plates, and is comparable in structure to 

 the corresponding tooth of the Indian elephant. The 

 carpincho is an inhabitant of the more tropical districts, 

 not extending southwards of Uruguay. Nearly allied are 

 the agutis [1 kisijprocta) and pacas [Ccdotjenys), collectively 

 constituting the family Dasiz/iroctida, which differ from 

 the cavies in that the folds of enamel only form notches 

 on the sides of the crowns of the cheek-teeth. The agutis 

 are rather delicately-built animals, ranging fi'om the con- 

 fines of Mexico to Paraguay, and represented by an outlying 

 species in the West Indies. The pacas, with nearly the 

 same distribution, are, on the other hand, much larger 

 and more heavily-built animals, characterized by the longi- 

 tudinal rows of light-coloured spots on the fur, and the 

 large bony capsules formed by the expanded cheek-bones. 



Another family 

 (Chiwhilllda) is 

 represented by 

 the beautiful 

 little chinchillas 

 {ChinchUhi) of 

 the Andes, so 

 esteemed on ac- 

 count of the 

 marvellous soft- 

 ness of their 

 pearly grey fur ; 

 by the much 

 larger Cuvier's 

 chinchilla {La<ii- 

 diuin), which is 

 also an inhabit- 

 ant of the Andes; 

 and likewise by 

 the well-known 

 viscacha ( Laiins- 

 tomus) which 

 lives in warrens 

 in the Argentine 

 pampas, and is 

 remarkable for 

 the habit of col- 

 lecting all kinds 

 of odds and ends 

 round the en- 

 trance of its 

 burrows. From 

 the similarity of 

 its habits, the viscacha is commonly believed to be a near ally 

 of the marmot, with which, however, it has no close affinity. 

 All the members of the family have long, bushy tails, very 

 soft fur, elongated hind limbs, and the molar teeth divided 

 by comple+e transverse folds of enamel into plates, as shown 



Via. 2. — Upper Surface of the Lower Jaw 

 of a jount; Viscacjia. The hinder part of 

 the left branch ia broken off. 



in Fig. 2. Sufficiently distinguished by their spiny 

 covering, the porcupines (Hystricida) are represented in 

 South America by two arboreal genera (Sijnethcres and 

 CIuEtomys), differing from all their allies by their prehensile 

 tails. 



The largest of all the families under consideration is that 

 of the octodonts {(htndontidce) which, as already mentioned, 

 has representatives in Africa, although the majority^of: the 

 forms are South American and West Indian. In addition 

 to other characteristics, these rodents have the clowns of 

 the molar teeth marked by infoldings of enamel on both 

 sides (Fig. 1), while there are generally five toes to each 

 foot. In form they are generally more or less rat-like. 

 Unfortunately, our limits of space permit only of a very) 

 brief reference to these forms. The typical representative 

 is the degu {(')cUidon) of Chili and Peru, which is a rat-hke 

 animal with a long tail tipped with a brush. Other species 

 inhabit Bolivia, which is also the home of^certain allied 

 rodents {Huhrocniiui) remarkable for having fur nearly as 

 soft as that of the chinchillas. Nearly related are the 

 burrowing tuco-tucos (Ctmomys) of South America, de- 

 riving their popular title from the bell-like cry uttered 

 as they work beneath the soil, and their scientific name 

 from the comb-like bristles with which the hind feet are 

 furnished. 



Passing over some smaller types, our next form is the 

 coypu (Myopottimus), which is a large aquatic form, with 

 beaver-like habits, found on both sides of South America, 

 and commonly known as the nutria. Eemarkable for the 

 bright red hue of its front teeth, the coypu, except for its 

 tail, is not unlike a beaver in general appearance, and is 

 commonly regarded by settlers in the Argentine as a near 

 ally of that rodent. In the West Indies the family is 

 represented by the large arboreal forms known as hutias, 

 most of which are included in one genus (Capromys) ; 

 although, on account of the complex structure of its 

 molars, one kind from Hayti and .Jamaica is separated 

 as Flagi'idon. These animals may be compared to 

 gigantic rats, one of them measuring twenty-two inches 

 exclusive of the tail. Six other genera are also found in 

 South America, most of them being smaller rat-like forms, 

 in some cases {Echinomys and Lanchovs) characterized 

 by the admixture of flattened, lance-like spines among 

 the fur. 



Limits of space preclude any mention of the mouse-like 

 members of the order peculiar to South America, and 

 this omission is of less importance since it is not improbable 

 that these forms are later immigrants fi-om the north. 

 Suflicient has, however, been said to show how extremely 

 peculiar and numerous are the rodents of the Neotropical 

 region, the whole of the genera belonging to the 

 porcupine-like group found in that part of the world being 

 absolutely confined to it, and the same being the case with 

 several of the families. Not only are these rodents remark- 

 able for the number of genera and species by which they 

 are represented, but they are likewise noticeable for the 

 large dimensions which many of them attain. Geological 

 investigations have shown that allied rodents— one of 

 which is stated to have attained dimensions equal to those 

 of an ox — inhabited Patagonia during the middle portion 

 of the Tertiary period, contemporaneously with the extra- 

 ordinary ungulates alluded to in a previous article. It is, 

 therefore, evident that all these mammals must have 

 obtained entrance into South America contemporaneously, 

 while they developed side by side during the period it was 

 cut off from the northern half of the continent. What 

 was the exact connection between these South American 

 rodents and the aUied African genera is at present uncer- 

 tain, but there are many facts which point to a former 



