Dr. Rengger’s Mummalia of Paraguay. 471 
anterior feet one pair, and on those of the posterior two pairs, of col- 
lateral, hard, elevated calli, which give name to the species. The Mus 
ongitar'sus, on the other hand, might at first sight be confounded with the 
Mus Musculus; but it differs in having the bristles that surround the 
mouth longer, that is to say, measuring nearly an inch in length; in the 
length of its tail compared to that of its body being as 1°22 to 1, 
while in the latter it is only as 1:08; and in the hinder feet being 
much longer, their whole length being 14 lines, of which the tarsz 
constitute 9. The Old Continent pests with which these two species are 
compared have also found their way to Paraguay, having been intro- 
duced by Spanish vessels ; they are now completely naturalized and 
extend their depredations to the plantations as well as the houses, but 
do not go far beyond the settlements of man, as the authour never met 
with them in unfrequented districts, or the isolated dwellings of the in- 
terior. Two species of Echimys are enumerated, viz. 40. Ech. spi- 
nosus, Desm., and 41. Ech. longicaudatus, Rengg. The latter, a single 
individual of which was taken in the northern part of the country, differs * 
but little from the preceding species, except in the length of its tail, 
which exceeds that of the body, while in Ech. spinosus it scarcely mea- 
sures half as much. The variation in colour between the two is by no 
means striking. There is little that requires particular notice in the 
remaining Rodentia; they consist of 42. Myopotamus Bonariensis, 
Comm., (Quiniya); 43. Sphingurus spinosus, F. Cuv., (Cuty) ; 44. Lepus 
Brasiliensis, L., (Tapiti) ; 45. Caelogenus Paca, (but one species, the 
Pay); 46. Chloromys Acuti, F. Cuv., (Acuti); 47. Hydrocherus 
Capybara, Erxl., (Capiygua) ; and 48. Cavia Aperea, Gmel. With 
respect to the latter Dr, Rengger maintains that it is specifically distinct 
from the domesticated Guinea-pig, and gives many excellent reasons 
for his opinion, taken from important differences in structure, economy, 
and habits—differences so remarkable that it is difficult to believe that they 
could have arisen solely from domestication in a distant country. 
The Edentata consist of five species of Armadillo, and two Ant- 
eaters, as follows: 49. Dasypus 6-cinatus, L., (Tatu-poyu); 50. Das. 
gymnurus, Illig., (Tatu-ay); 51. Das. 9-cinctus, L., (Tatu-hu) ; 52. 
