1882.] 



ANATOMY OF ERETHIZON DORSATUS. 



279 



central is larger than the left lateral ; and that the Spigelian lobe is 

 larger both relatively and absolutely, and is also distinctly notched ; 

 and that the caudate lobe is larger and more slender. How far 

 these may be individual peculiarities I am of course unable to say. 



The siileen was very different in form from that of Hystrix 

 javanica. In the latter it is much elongated, while in Erethizon it 

 is oval in shape and somewhat flattened. Its length is 3"'3, its 

 breadth 2". 



The lungs consist of three lobes on the right side and two on the 

 left, whereof the upper left lobe is divided by two deep notches. 



Fig. 8. 



The brachial plexus of Erethizon dorsattis, 



I-VII, cervical vertebra ; 1, 2, 3, 4, the first four ribs; cir, circumflex nervo ; 

 Ex. cut, external cutaneous ; In.c, internal cutaneous ; M, median, M.sp. 

 musculo-spiral ; Ul, ulnar. 



The heart is very rounded at its apex. 



The aorta gives off a large innominate artery, from which the 

 right subclavian and the two common carotids arise. The left sub- 

 clavian is given off separately. 



