340 A NEW MYLODON. 



in height, as against 150 and 127 respectively for P. nebrascensis as given by 

 Brown. Both calcanea are imperfect but present no especial peculiarities. 

 The hind foot was provided with four toes, of which the two inner bore large 

 claws, as in other species of the genus. Owen considers that it is digit 1 which 

 is wanting. Digit 2 has the smaller and digit 3 the larger claw. That of the 

 former (Plate 3, fig. 13) is straight, conical, and somewhat flattened vcnlrally. 

 An angular ridge forms the lateral boundary between the upper and tlie l()\\(>r 

 surface. A large thickened disk of bone is present at the base of the claw vcn- 

 trally, below the level of the proximal cotylus. The extreme length of the 

 phalanx is 77 mm. ; its greatest depth at the anterior end of the ventral disk 34 

 mm. The basal sheath of thin bone is largely broken away. The claw of digit 

 3 (Plate 3, fig. 12) is very large, next in size to the great claw of the manus. Its 

 shape, however, is different, for instead of being practically straight in dorsal 

 view its long axis is bent in a shght arc inward. The distal third is marked with 

 a shallow dorsal groove, and the tip is much flattened dorsoventrally. Com- 

 pared with the corresponding bone in the mounted specimen of M. robustus in 

 the Museum, it is much more slender and laterally compressed. Its greatest 

 length is 167 mm. ; its depth at the base 48 mm. 



The two phalanges of digit 4 are present, of which the terminal (Plate 3, 

 fig. 14) is a short, bluntly pyramidal bone 42 mm. long, with a deep notch ven- 

 trally near the base for tendinous insertion. It articulates with the somewhat 

 square and anteroposteriorly compressed basal phalanx whose ventral border 

 is eraarginate for the passage of a tendon, and whose posterior face is deeply 

 hollowed for articulation with metatarsal 4. The terminal phalanx of digit 5 

 (Plate 3, fig. 15) is similar but smaller. 



Dermal Ossicles. — Accompanying the large bones of the body are a number 

 of small dermal ossicles, which are mainly round or ovoid in shape, or occasion- 

 ally lozenge-shaped. The round ones vary from 3 to 8 or 9 mm. in diameter; 

 one elongate ossicle is 12 nmi. in length by 5 mm. in transverse diameter. An- 

 other is flattened and squarish, about 8 mm. on a side. These are very different 

 in shape from the dermal ossicles described by Sinclair (1910) for Paramylodon. 

 The latter were found overlying the scapula, and are apparently larger, more 

 often squarisli or rhomboid in outline, or u-regularly shaped. 



Comparison with Mylodon soda lis Cope. 



In 1878, Cope named and described Mylodon sodalis as a new species, 

 basing his account particularly on an ungual phalanx "from the Pliocene of 

 Oregon," and briefly mentioning other proximal phalanges. Later (1889) 



