THE AGUARA WOLVES. 945 
vertical opening, but liable to assume the rounded 
shape in a moment; and this effect being generally 
produced under all circumstances of emotion or par- 
tial obscurity, in all the nocturnal, the criterion 
escapes notice, unless it be determined by dissec- 
tion, an operation demanding manual skill and pre- 
vious anatomical education; these requisites not 
being always possessed by travelling investigators, 
leave doubts which can be removed only by such 
establishments as zoological gardens, where species 
can be studied living and be dissected after death. 
South America, when first discovered by the 
Spaniards, was possessed of canines absolutely indi- 
genous, some universally wild and others liable to 
be partially reclaimed ; all more nocturnal than the 
former dogs and less so than true foxes. Of the 
first class there is perhaps only the Chrysocyon 
before described; in the second, although clearly 
distinguishable into two groups, alike furnished 
with rounded foreheads, there are general indica- 
tions of a more placable nature. The eyes of some 
are considered circular; they have comparatively 
longer and bulkier bodies and shorter tails, while 
the others with the external form of foxes, the nose 
still more pointed and brushes even longer and 
more ample than these animals, have indeed the 
pupils of the eyes vertically contractile, but so im- 
perfectly, that they become elliptical only when the 
head is forcibly held against a strong light; they 
are hence crepuscular, not nocturnal, unless there 
be a clear moonlight. Their propensities to rapine 
