692 OS THE AlfATOilT OE ATHEUURA AFEICAIfA, [NoV. 20, 



plantar surface. I was unable to satisfy myself as to the nerve- 

 supply of the lumbricales. 



The pudic nerve comes almost entii-ely from the 2n(i S. and 

 supplies the muscles and skin of the perineum. 



In comparing the plexuses of Atlurura with those of Evetltizon 

 as figured by Mivart ', it will be noticed that the brachial plexus 

 of the latter receives no branch from the 5th C. as it does in 

 Ailierura and Man, but that all the branches of the plexus are as 

 easily traced to their origins from the spinal cord as they are in 

 Atlierara. In the sacral plexus the small sciatic of Ereiliizon seems 

 to rise from the same place as the pudic of Aiherura, viz, the 1st 

 and 2nd sacral, but then no indication is given in the figure of the 

 origin of the pudic in Erethizon. 



The nerves of a specimen of Hystrix cristata, which I dissected 

 in order to compare with those of Atherura, show a striking 

 resemblance to the latter animal. 



The following are the only differences I noticed : — The circum- 

 flex comes from the 6th and 7th C. instead of the 5th aud 6th. 

 The external cutaneous communicates with a branch of the median 

 going to the brachialis anticus and sends no cutaneous branch to 

 the forearm. The median rises from 5th, 6th, 7th, and 8th C. and 

 1st D., and receives a large branch from the external cutaneous, 

 which branch is bou^ud up with the median, and eventually comes 

 off to supply the outer side of the forearm. The nerves to the 

 teres major and latissimus dorsi which I failed to notice in 

 Atherura rise in ffi/siruv from the circumflex. 



The supplies of the fingers and toes are identical in both animals. 



The arrangement of the nerves in the hand and foot already 

 mentioned seems of some interest from the point of view of 

 variation. 



In Man the ulnar supplies one finger and a half on the palmar 

 surface, and the external plantar one toe and a half on the plantar 

 surface. In Atherura and Hystrix neither of these nerves supplies 

 any of the fingers or toes. 



I do not think that this arrangement is peculiar to the Hystricidce, 

 because it occurs also in the Hamster and possibly in other Rodents. 

 Since Man and the Porcupines agree in having the same arrange- 

 ment of nerves in the hand as in the foot, but differ in that 

 arrangement, it looks as if the cause that brought about the change 

 of arrangement was identical for the two extremities. 



-"to^ 



P. Z. S. 1882, p. 279. 



