&LOTH. 
his account, and fallen inta some error. In- 
deed, his own general description of the two 
species, affords sufficient demonstration that 
they ought to have been severed. " Though," 
says h€, ** they resemble each other in manv 
respedtsj they differ, both externally and in- 
ternally, by characters so marked, that it is 
impossible not to recogni-se them as very dis- 
tinct species. The Unau, or Two-Toed 
Sloth^ has no tail, and only two claws on the 
fore- feet; the AT, or Three-Toed Sloth, has 
a tail, and three claws on all the feet. The 
muzzle of the former is longer, the front 
more elevated, and the ears more apparent^ 
than those of the latter. Their hair is also 
very different. The stru6lure and situation of 
some parts of their viscera are likewise dif- 
fcrent* But the most remarkable difference is 
derived from tliis singular circumstance, that 
the Unau has forty-six ribs, and the Ai only 
twenty-eight, which shews them to be species 
very remote from each other. This number 
of ribs in the body of an animal so sliort, 
is. an excess,, or error, of Nature ^ for no ani- 
mal,, however large, has such a number of 
ribs- The l^lcphaut has only forty, the Horse 
diirty-six^ 
