THE PELVIC LIMB 



In two specimens of sea-lion examined, one fresh and one preserved, 

 the relaxed posture of the foot was latero-craniad at an angle of about 

 45 degrees with the body axis. In life, however, an angle of approxi- 

 mately 90 degrees may frequently be assumed, and in young fur seals 

 observed the latter was the invariable posture. This facilitates the plac- 

 ing of the feet sole to sole when in the water. In the Otariidae the 



FIGURE 50. Pelvic bones of sirenians. Above is illustrated progressive develop- 

 ment according to the fossil evidence: (a) Eotherium (Middle Eocene) ; 

 (b) Eosiren (Upper Eocene) ; (c) Halitherium (Middle Oligocene) ; (d) 

 Metaxytherium (Middle Miocene); (e) Halicore dugong (recent); (/) 

 Halt core tabernaculi (recent); and (g) Trichechus latirostris (the manati) 

 ( redrawn from Abel ) . 



interdigital membranes are capable of practically no expansion, and the 

 foot is correspondingly narrow as compared with that of a seal. It is 

 relatively very long, however, because of the predigital cartilages, as in 

 the manus. But in the foot, these can be folded back against the palm 

 so that the body may be scratched with the slender nails of the three 

 middle digits. The nails of the first and fifth digits, are, however, ru- 

 dimentary like those of the manus. 



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