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GROUP SECOND. 
We shall take, to characterize this eroup, the 
Argozoum, from épyic, swift, winged. 
Of this genus there are two species, the larger of 
which is the Arcozoum Disparipiairatum. It is 
leptodactylous, and remarkable for the length of the 
middle toe. We have another species, which is 
smaller than the last named, and in which the toes 
are nearly of equal length; hence called Arcozoum 
PARIDIGITATUM. 
The other genus of this group is the PLaryPTEeRNa, 
and our specimen is named Deaniana. This genus is 
remarkable for the width of the heel; hence the 
name, from ziaric, broad, and xrépvn, a heel. It has three 
toes like the other genera of this group. 
GROUP THIRD. 
This and the succeeding group are tetradactylous ; 
having one toe behind, three forwards. 
The third group is leptodactylous; foot usually 
small, but sometimes of medium size. Of it we have 
two specimens, viz.: OrnirHopus GALLINACEUs, and 
