APTERODON MACEOQNATHUS. 



231 



M. 8504. Distal end of right humerus. Figured on PI. XIX. figs. 7, 7 a. Closely similar to 

 C. 9445. 



M. 8440. Distal ends o£ two similar humeri. 



C. 8845. Right tibia, wanting the epiphyses (text-fig. 75). The bone, as a whole, is strongly 

 curved, the convexity being anterior. The cnemial crest (en.) slopes away and 

 probably its upper end was overlapped by the patella. It extends about halfway down 

 the bone, and terminates in a rugose prominence for the attachment of a powerful 

 muscle. The upper half of the shaft is trihedral. On the inner face just below the upper 

 end there is a long roughened depression for muscle-attachment (m.). The posterior 

 face at the upper end of the bone is concave from side to side. Towards the distal end 

 the shaft widens out a little, but in this specimen the articular region is wanting. On 

 the whole, this bone seems to lend some support to the idea that this Creodont may have 



Text-fig. 76. 



Eight astragalus of (?) Apterodon macro gnathus : A, from above ; B, from below. 



caL, facet for calcaneum ; ect., ectal facet ; /., astragalar perforation ; Jib., surface for fibula ; nav., facet for 

 navicular; sus., sustentacular facet ; <i6., surface for tibia. Nat. size. 



been more or less aquatic in its habits. The well-marked rugose surface for the 

 attachment of muscles at the inner side of the proximal end of the shaft (m..) seems to 

 occur also in some Seals and in Lutra, while that marked m' in the figure may 

 correspond with a somewhat similarly situated rugosity in some Seals. The dimensions 

 (in centimetres) of this bone are : — 



Length . . . IS'-i 



Width of proximal articulation 3'7 



Antero-posterior width of shaft at muscular prominence . . 2-5 



M. 9258. Plaster cast of the al)ove specimen. 



Made in the British Museum. 



C. 8116. Right astragalus (text-fig. 76). The trochlear surface (i«6.) is very slightly grooved ; on its 

 inner side it is produced backwards in a sort of tongue to the extreme hinder border. 

 At the angle between the outer edge of this backward extension and the posterior border 

 of the outer half of the trochlea is the large upper opening (/.) of the astragalar canal. 



