MYOLOGY 41 



emerging superficial to that muscle and joining the re- 

 mainder of the levator at the dorsal border of the scalenus. 

 In Homodontomys the emergence from the scalenus is at a 

 point about midway between the dorsal and ventral borders 

 of the latter. The muscle converges to a fleshy insertion 

 along the medio-dorsal border of the scapula between the 

 insertions of the rhomboidii and serratus magnus. 



Neotoma is very similar, except that the caudal slip 

 emerges ectad of the scalenus well towards the dorsal 

 border of the latter. In Teonoma the original width is 

 about 30 mm., the increase of five millimeters compensating 

 for the fact that it arises from the first five ribs, and it 

 emerges from the scalenus considerably nearer its ventral 

 border. 



The innervation of this muscle is from the cervical 

 plexus — not from the brachial plexus as would be the case 

 were it a part of the serratus. 



Mm. intercostales externi (fig. 10). The external in- 

 tercostals join each rib to its neighbor. The fibers have 

 a tendency to extend cranio-dorsad, though this is hardly 

 true in the case of the more caudal series. Until after the 

 seventh rib is passed they do not extend between the costal 

 cartilages, but only between the true ribs. After that the 

 external intercostals occur between the cartilages as well. 

 The fibers passing cranio-dorsad from the more dorsal 

 part of the third rib are not inserted upon the second, but 

 extend farther craniad and are inserted upon the first rib. 



Mm. intercostales interni (figs. 7, 10). These are 

 situated chiefly deep to the last, to which they are similar 

 except that the fibers have a tendency to pass cranio- 

 ventrad. Without removing the external intercostals 

 they are to be seen only where they join the first seven 

 costal cartilages one with another. 



In Teonoma the diaphragm is placed farther craniad 

 than in the other two subgenera, being undoubtedly so 



