60 FIELD MUSEUM OF NATURAL HISTORY ZOOLOGY, VOL. XIV. 



although better comparisons than are here possible might prove this 

 to be the case. It is worthy of particular note that it has a considerable 

 number of points in common with the extraordinary form Notoryctes 

 and that, as in Notoryctes, some of its most exclusive features as a mar- 

 supial are suggestive of edentates and insectivores. Among such are 

 the divided trapezius, the dorso-cuticularis, the absence of a pronator 

 quadratus, the sesamoid origins of the supinator and the short flexors 

 of the hind foot, and the peculiar sartorius. It is also to be noted that 

 some of the resemblances between C&nolestes and Didelphis not shared 

 by most other marsupials are however to be found in other mammals, 

 especially edentates, and therefore cannot be taken as certain indications 

 of close relationship between C&nolestes and Didelphis. The well-de- 

 veloped pedal extensor hallucis brews and the flexor accessorius pedis 

 are perhaps examples of this kind. 



The muscles of the legs and feet in Ccsnolestes are adapted to a terres- 

 trial, almost cursorial, life. The leg muscles have short thick fleshy parts 

 and very long tendinous extensions, relatively longer even than in such 

 terrestrial forms as Phascologale, and in this respect are perhaps most 

 similar to those of the saltatorial but otherwise generalized Australian 

 polyprotodont Antechinomys , the myology of which has not been 

 thoroughly described. The proportion of tendinous to fleshy parts is 

 about as 60 to 40 and the outline of the leg thus resembles that of a 

 digitigrade animal. It is markedly different from that of Didelphis in 

 which fleshy extensions reach nearly or quite to the carpus and tarsus. 

 Specialization for terrestrial life has proceeded far beyond that in 

 Peramys whose habits are presumably not greatly different from those 

 of C&nolestes but whose musculature is only slightly different from that 

 of Didelphis. 1 The absence of the pronator quadratus is not accompanied 

 by such reduction of other muscles as might be expected in view of the 

 facts that otherwise a large number of muscular elements are present in 

 the limbs and that their distinctness from each other is marked. There 

 is some reduction of the intrinsic muscles of the feet, especially in the 

 adductorial sets, and the grasping power is distinctly limited. 



All the important muscles have been worked out with considerable 

 care, but the nature of the material, the small size of the animal, and the 

 lack of comparative material, have made it impossible to be certain of 

 relations in all cases. Such comparative notes as are ventured are based 

 on examination of the scattered literature and the comprehensive work 

 of Leche in Bronn's Thierreich. Comparison of actual specimens has 

 only been possible with Didelphis, Marmosa, and to some extent with 



1 No careful study of Peramys has been possible, but cursory examination of its 

 feet and legs indicates close similarity to Didelphis. 



