178 BR. E, BEOOM OK THE STEUCTITEE AND [June 4, 



more curved than in U. gracilis, and there is thus formed a larger 

 interosseous space. 



There does not seem to have been an ossified patella in Udenodon. 



Tarsus. 



The tarsus of the right side (PI. XVI.) has its under surface 

 well shown, and though a dorsal view would have been more 

 satisfactory, a good idea is obtained of the structure of the joint 

 even though a little doubt may remain on one or two points. The 

 tarsus of the left side is so twisted that it is difficult to be sure of 

 some of the elements. 



Articulating with the tibia and fibula respectively (PL XYII. 

 fig. 5) are two large elements^ — manifestly the tibiale (tl.) and the 

 fibulare ifl.), with a small bone lying between, doubtless the inter- 

 medium (■».). The distal row of the tarsus is formed by five 

 tarsalia ; while in the centre, between the distal row and the 

 tibiale and fibulare, is a ceutrale (c), small as displayed on the under 

 surface, but probably of much larger size on the upper. 



The tibiale, or astragalus, as displayed, is a fair-sized somewhat 

 pentagonal bone with the upper and outer angle sharp and pro- 

 duced. By its proximal and probably its inner face it articulates 

 with the tibia. On its outer face the little intermedium comes 

 between it and the fibulare, but it is probable that an articulation 

 between the two large elements takes place above and distally to 

 the intermedium. On the distal border of the tibiale lies the small 

 centrale. It is probable that the tibiale does not articulate with 

 any other element. As the tarsus is displayed in the specimen, 

 there appears to be no element between the 1st tar sale and the 

 tibiale, and one might infer that the tarsale had articulated with 

 the tibiale, and that these elements are slightly displaced ; but it 

 seems much more probable that what appears to be a very small 

 centrale is merely a projection, showing on the under side, from 

 a moderately large centrale which fits in between the 1st tarsale 

 and the tibiale, as does the navicular in mammals. 



The intermedium (i.) is a very small element, at least so far as 

 displayed, fitting in between the tibiale and the fibulare, and 

 articulating with these two elements and with the fibula. It is 

 possible that the element may not be a true intermedium, but a 

 small sesamoid bone ; its being deeply implanted, however, between 

 the other tarsal elements, and its occupying the exact position 

 where an intermedium would be looked for, leads me to believe 

 that I have rightly interpreted it as that. 



The fibidare is a large, elongated, four-sided element, nearly as 

 large as all the other tarsal elements together. Its proximal side, 

 by which it articulates with the fibula, is the shortest of the 

 four. The inner side, which is half as long again as the proximal, 

 articulates with the intermedium, the tibiale, and the centrale. 

 The distal end of the element, which is a little shorter than the 

 inner side, but much broader than the proximal end, articulates 

 with the fourth and fifth tarsalia and with the fifth metatarsal. 



