THE PACA OF BRAZIL. 
135 
the following observations relate, does not appear to have 
been hitherto dissected. 
Daubenton states, that the Paca possesses clavicles, and, 
in his figure of the skeleton, he has represented them as 
complete, and uniting with the acromion of the scapula. 
If, however, the clavicles had been complete in this animal, 
it would have formed an exception to the group of Ameri- 
can Glires, to which it belongs, as they are incomplete in 
the Agonti, the Guinea-pig, and the Capibara. Cuvier has 
placed the Paca among the Rodentia that possess imperfect 
clavicles, as he has done the Capibara, which he states in 
his Leg. d'An. Comp. (i. to have no clavicle whatever. 
Later writers have followed his example in giving imperfect 
clavicles to the whole group. In the Paca the clavicle con- 
sists of a small cylindrical bone, about a line in diameter, 
1| inch in length, considerably enlarged at each end, and 
which does not reach either the sternum or the scapula. 
A cylindrical compressed cartilage, three-fourths of an inch 
long, is attached to the sternal extremity of the clavicle, 
and plays loosely on the inner surface of the sternum in a 
wide capsule. There is no articular surface at the upper 
part of the sternum for the attachment of the clavicle. 
The scapular extremity of the clavicle has a soft irregular 
piece of cartilage only two lines long attached to it, which 
is only connected by cellular substance with the muscles of 
the neck, and the acromion of the scapula has no articular 
surface. The muscles of this animal had a pale and wast- 
ed appearance, and there was scarcely any adipose sub- 
stance either on the external or internal parts of the body, 
which may have been owing to the lingering consumption 
of which it died. Numerous tubercles existed in the sub- 
stance of the pleura costalis at the sides of the vertebrae ; 
they were spread over the surface and through the whole 
texture of the lungs to such an extent, as to cause large 
