1914] Taylor: Aquatic Adaptation in the Carnivora 483 



the tail is used as a rudder. The shape of the tail and the 

 presence of the so-called flanges upon it laterally have led to 

 the suggestion by Lull 3 ' that they are homologous to the ex- 

 panded flukes on the tails of certain of the Cetacea and Sirenia. 

 the posterior position of the flukes in these groups being a mech- 

 anical adaptation which has been accelerated in its appearance 

 so as to be embryonic. 



Vertebrae 



General Characters. — The form of the vertebrae in the sea- 

 otter is different from that in the river otter, in that the inter- 

 vertebral foramina are larger, especially posteriorly, the zyga- 



Figs. 7-9. Lateral views of selected vertebrae of river otter, sea- otter, 

 and seal. x%. 



Figs, 7a, lb and 7c. Vertebrae of river otter (Lutra canadensis) . Fig. 



la, fifth cervical; lb, third lumbar; 7c, fourth caudal. 

 Figs. 8a, 86 and 8c. Vertebrae of sea-otter (Latax lutris nereis). Fig. 



8a, fifth cervical; 8b, third lumbar; 8c, fourth caudal. 

 Figs. 9a, 9b and 9c. Vertebrae of seal (Phoca vitulina). Fig. 9a, fifth 



cervical; 9b, third lumbar; 9c, fourth caudal. 



35 Lull, B. S., ' ' Eelation of embryology and vertebrate paleontology, ' ' 

 Popular Science Monthly, vol. 77 (1910), p. 153. 



