214 



ANATOMY OF THE WOOD RAT 



becomes fused to the tibia is 57.7 per cent of the tibial 

 length in Homodontomys, 63.2 in Neotoma, and 58.9 per cent 

 in Teonoma. 



The total length of the hind foot in the articulated skele- 

 tons averages 37.5 per cent of the functional length of leg in 

 Homodontomys, 39.5 in Neotoma, and 40.5 per cent in 

 Teonoma. The significance of this sUght variation is in 

 doubt. The ental aponeurosis of the gastrocnemius lateraUs 



TABLE 4 

 Comparisons of Non-muscular Soft Parts of Three Subgenera 



Ventral dermal gland 



Oral bristle area 



First ridge of oral dia- 



stemal ridging 



Parotid gland 



Submaxillary gland 



Muscularity of stomach . 

 Small intestine 



Liver 



Length of caecum 



Colic loops 



Rectal tract 



Anal gland 



Thyroid gland 



Glans penis 



Convergence of uteral 

 horns 



HOMODONTOMYS 



absent 

 flat 



norm 

 norm 

 norm 

 norm 

 norm 



norm 

 norm 

 norm 

 norm 

 norm; no 



ducts 

 norm 

 intricate 



V-shaped 



absent 

 higher 



larger 



norm 



norm 



more 



shorter 



larger 

 norm 

 fewer 

 shorter 

 smaller; ducts 



present 

 norm 

 cylindrical 



intermediate 



present 

 highest 



largest 



smaller 



larger 



most 



broader; long- 

 est 



much largest 



longer 



fewer 



longest 



largest; ducts 

 in 9 



larger 



acute 



U-shaped 



is more crumpled in Homodontomys than the other two 

 animals, and the muscle fibers more definitely pennated 

 thereon. This indicates increased power in this muscle, 

 which is the strongest one of those operating over the cal- 

 caneum to extend the foot. This is as might be expected 

 from the fact that the longest tibia occurs in this genus. The 

 double insertion of the peroneus digiti quarti in Teonoma, 



