TU PN op aci Fool PEPERIT 
Mr. Brooxzs on a new Genus of the Order Rodentia. 101 
The Rabbit . . . 7 lumbar vertebrz. 
Marmot . 
Urson 
Agouti 
Coypus . 
Capromys 
DAOIN 
HE 
Hence it appears, that in the number of the ribs, and of the 
lumbar vertebre, the Lagostomus agrees with the Jerboa, the 
Squirrel, and the Rabbit. From the former of these its distinc- 
tions have been already pointed out. From the Squirrel it dif- 
fers amply in the want of the rotatory motion of the bones of 
the fore-arm, and in the number of the toes, which in that animal 
are five upon each foot. In the Rabbit the fibula is anchylosed 
with the tibia a little below its middle, as in the Jerboa,—a cir- 
cumstance which takes place also in the Rat. From the Agouti, 
with which it corresponds in its tridactyle hinder extremities, it 
is distinguished by the number of the ribs and of the lumbar 
vertebra, as well as by various other particulars of the osteology. 
In the Helamys there are five toes to the fore-feet, and four to 
the hinder. With the exception of this animal, of the Rabbit, 
and of the Jerboa, the tibia of Lagostomus exceeds in com- 
parative length, that of any of the other Mammalia enumerated 
above. : 
One circumstance which has been noticed in the anatomical 
description is worthy of particular remark ;—the bony union of 
the radius and ulna in an animal, which, from the testimony of 
accurate observers, who saw it during its life, employed its an- 
terior extremities in conveying its food to its mouth. This struc- 
ture, so far as I am acquainted with the osteology of the Mam- 
malia, is perfectly unique. It has been hitherto regarded as 
quite at variance with the existence of clavicule, most of the 
quadrupeds 
