192 
MACROrODID.E. 
Kangaroos,— the three central toes proportionately longer than 
we find them in Macropits, and the lateral toes smaller; the 
nails, moreover, are of a different form : in Macropus they 
are broadest, and concave beneath, whilst in Hypsiprymmis 
they are much compressed, solid, and broadest above. These 
differences, observable in the structure of the fore foot ami 
claws, are connected with certain differences in the habits.of 
the species of the two divisions. Whilst the true Kangaroos 
browse upon the herbage, the Rat-Kangaroos, we learn, feed 
much upon the roots of certain plants, which they scratch up 
with their fore feet. In the hind feet no constant difference 
is perceptible. In the structure of the skull and teeth there 
are many differences worthy of remark:—The frontal bones 
are larger in Uypsiprijmutts than in Macropus ; the muzzle is 
more compressed, and more pointed at the extremity; die zygo¬ 
matic arch is much more slender, its vertical diameter being 
considerably less; the pterygoid processes are less developed; 
the intermaxillary bones are less produced: a vertical line 
dropped from the tip of the nasal bones, in the animals under 
consideration, would, in most species, very nearly,touch the 
front edge of the foremost incisor, but the same tooth in 
Macropus would be found advanced considerably beyond 
the corresponding line. The auditor)* bulke, which, as Prof. 
Owen has pointed out, are, in almost all the Marsupialia, 
formed by the expansion of the great ahe of die sphenoid, 
and not by a portion of the temporal bone, as in the 
Rodents, here assume a hemispherical form. I have not met 
with this, as it were, inflated auditory chamber, in any of 
the species of the Ma crop us division, excepting in tbe 
Lag or chest vs Icporoides and the L. eonspicitlatusK With 
1 Since my account of the species Lagorchoxtr* was printed, I hare had an 
opportunity of examining a skull of the L. conspicillattis, contained in Mr. 
Gould’s collection: this ditTcrs much from the skull of L. leporoide*. The 
muzzle is shorter and broader, the zygomatic arch docs not project so suddenly 
