60 



R. J. Anderson, 



as ihe rib is traced up. Rapid decrease in the 9*^ and in the U'^ 

 and 12*'! an increase takes place. 



In the middle ribs the tangential breadth commences to exceed the 

 radial at a point about the middle of their length although the 

 actual breadth is less here than farther forwards. 



The inner border of the first and the lower parts of the anterior 

 borders (Va — ^/3) of the following ribs are sharp. 



The breadth of the 8*^ ribs is greater at a point 130 mm., above 

 the lower end than above or below that point. 



Lutra Vulgaris. The first rib is very strong and has a single 

 curve. The other ribs are flattened from before back above and their 

 inner surfaces turn back inferiorly so that a large triangular surface 

 turns backwards and outwards below see Beaver. 



The Beaver. 



The ribs have considerable radial breadths (PI. II. fig. 3). The 

 posterior surfaces of the 4*^^, 5*^, 6*^, 7*^ and S*'^ become the outer below 

 and here the rib diameter becomes considerably greater. 



The distance of the first dorsal transverse process from the last 

 ip 17,5 cm. 



The following table gives the measurements. 





1 



2 



3 



4 



5 



6 



7 



8 



9 



10 



11 



12 



13 



14 



A 



53 



68 



80 



100 



110 



120 



120 



115 



112 



110 



110 



105 



100 



95 



B 



15 



2a 



40 



60 



60 



104 



120 

















C 



10 



7 



8 



9 



10 



10 



11 



10 



6 



5 



5 



5 



6 



5 



D 



— 



— 



— 



— 



— 



— 



— 



— 



— 



— 



— 



— 



— 



— 



Ë 



8 



7 



7 



9 



7 



7 



7 



5 



5 



5 



5 



5 



4 



4 



Lepidus timidus. 



The radial and tangential breadths of the lower 5 ribs are nearly 

 equal. 



From the second to the sixth, the tangential breadths exceed the 

 radial;, except near the tubercle. 



These ribs show a thickening all along the middle and have very 

 sharp anterior margins expecially in their lower thirds. 5 mm., 8 mm., 



