CENTRAL NERVOUS SYSTEM OF ARMADILLO. 293 



The axillary nerve (PI. XXVI., Ax.} arises from the fifth and 

 sixth cervical nerves. It supplies some muscles in the upper arm. 



The radiales nerve (PI. XXVI., Rad.} is one of the three 

 nerves that supply the lower arm and hand. It arises from the 

 sixth, seventh, and eighth cervical nerves. 



The incdianns nerve (PI. XXVI., Med.} also principally sup- 

 plies the muscles of the forearm and hand. It arises from the 

 seventh, and eighth cervical, and the first thoracic nerves. 



The ulnaris nerve (PI. XXVI., Uln.} is the third lower arm 

 and hand nerve. It arises from the eighth cervical, and first 

 and second thoracic nerves. 



(r) Thoracic Plexus. From the first, second, and third thoracic 

 nerves arise three ventral branches which pass out laterally and 

 unite into a little separate plexus (PI. XXVI., X.} Then this 

 plexus gives off three main branches which subdivide again and 

 again. All of these branches supply the great lateral skin muscle 

 which is attached along the whole length of the armor. A 

 plexus like this, to my knowledge, is not present in any other 

 mammal. It has probably arisen because of the great develop- 

 ment of the large skin muscle, which attaches to the sides of the 

 armor and functions in drawing the animal together in a ball. 

 Because of its origin from the thoracic nerves, I have taken the 

 liberty of naming it the thoracic plexus. 



The remainder of the thoracic nerves are arranged similarly 

 to those of other mammals. They divide into two branches 

 almost immediately after leaving the intervertebral foramina. 

 The dorsal branches supply the superficial muscles of the back, 

 while the ventral branches run along the ribs as the intercostal 

 nerves. 



(d] Lumbar Nerves. The first three lumbar nerves take no 

 part in the formation of the lumbo-sacral plexus. The ventral 

 branch of the first lumbar nerve divides into two branches, the 

 ilio-hypogastric (PI. XXVI., //. //)'/.), and the ilio-inguinal (PI. 

 XXVI., //. Ing.*}. The ventral branch of the second lumbar 

 nerve forms the genito-crural nerve (PI. XXVI., Gen. Cr.}. 

 The third lumbar nerve forms the external cutaneous nerve (PI. 

 XXVI., Ext. Cut.}. 



(e) Luinbo-Sacral Plexus. The lumbo-sacral plexus is com- 



