MAY, 1921. AMERICAN MARSUPIAL, CENOLESTES OSGOOD. 95 



the ratio given being that of the femur to the tibia. From this table it 

 is seen that this ratio is less in Ccenolestes than in any other forms ex- 

 amined except the Giant Kangaroo and that it is approximated only by 

 saltatorial forms. 



Length of Length of Ratio of Femur 

 Femur Tibia to Tibia 



Macropus giganteus 265 465 57 



Csenolestes obscurus 14.3 22.5 63.5 



Sminthopsis crassicaudata ... 13.6 19.8 68 



Antechinomys laniger .... 19 27 70 



Petrogale xanthopus 153 195 78 



Phascologale cristicauda .... 23.3 28 82 



Marmosa mexicana 23 26 . 8 85 . 8 



Dasyurus viveninus 65 73 89 



Myrmecobius fasciatus .... 45.5 51 89 



Perameles nasuta 64.5 69 93-4 



Peramys domesticus 21 22 95-4 



Philander philander 35-4 37 95-6 



Didelphis virginianus 76.8 78 98.4 



Sarcophilus harrisi 91-5 9^-5 loo 



Trichosurus vulpecula .... 94-5 9 2 -5 102.1 



Thylacinus cynocephalus . ... 195 190 102.6 



Phascolomys ursinus 175 133 131 



Phascolarctos cinereus .... 155 115 134 



BONES OF THE FOOT. 

 Plate XVI, Figs. 2-5. 



The foot is long and narrow, the tarsus being relatively short and 

 the metatarsus very long. It has general resemblance to the foot in 

 Dasyurus, Sminthopsis , Antechinomys and similar forms, but its structure 

 shows decided approach to that of Perameles and the macropods. 

 Although the hallux is present and relatively well developed (longer 

 than in Dasyurus, for example) the relations of the ankle joint are more 

 adapted to cursorial life than in some of the forms in which the hallux 

 has nearly or quite disappeared. This is shown especially by the astra- 

 galus which is somewhat intermediate between that of the pedimanous 

 marsupials and that of the highly saltatorial forms. Although it retains 

 general similarity to the astragalus of Didelphis, Sarcophilus, Myrme- 

 cobius, Phascologale and various other polyprotodonts,it shows a distinct 

 approach to the condition in the Macropodidae in which there is one 

 large trochlea and facets on either side, nearly at right angles, for the 

 outer malleolar parts of the tibia and the fibula. The body of the 

 astragalus stands at right angles to the neck and head and scarcely 

 exceeds them in size. The neck is not constricted to differentiate it 



