PLATE 5 
Cephalic view of the first (upper row) and the thirteenth (lower row) thoracic 
vertebrae; about nine-tenths natural size. 
Figs. 1 and 5. No. 19229, Castor fiber. 
Figs. 2 and 6. No. 210, Castor canadensis phaeus. 
Figs. 3 and 7. No. 4347, Castor canadensis belugae. 
Figs. 4 and 8. No. 16385, Castor subauratus. 
Note that in swbauratus and fiber the first thoracic vertebra, figures 1 and 4, 
has a broader neural canal, and that in subauratus, figure 4, the height is greater ; 
that the ‘‘hauteur totale du corps de la vertébre’’ in the first thoracic vertebra 
is greater in subawratus and fiber, and that on the thirteenth canadensis shows 
this measurement to be greatest; that there is a tendency for fiber and canadensis 
to have larger centra. 
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