Description of the Bones of a new Fossil Animal. 77 



cets by a vertical central ridge, continued above into a projection 

 of the superior posterior border of the phalange, as in the raega- 

 lonyx and orycteropus. Yide Plate I, figs. 11, 12, 13, 14 

 The dimensions of the claws are as follows : 

 Length of the longest, measured along its base, (the superior 

 posterior part being destroyed,) ... 4^ inches. 

 Next in size, similar measurement, . . . 3 T \ " 

 The same along its superior border, . . 3J- " 



Third, " " "... 3 " 



Fourth, " " "... 2| " 



Varying in depth from one to two inches ; in breadth from one 

 inch to half an inch. 



Tibia. — Two nearly perfect have been preserved, one belong- 

 ing to the middle sized, the other to the smallest individual, and 

 the latter to the left, leg ; we shall describe the latter, more par- 

 ticularly as it articulates aptly with the astragalus, the only bone 

 of the tarsus obtained. The tibia is a short thick bone, depress- 

 ed in its shaft, and thinnest on its exterior border, and much en- 

 larged at each end ; the superior articulating surface presents a 

 simple, shallow, ovoid disk, or glenoid cavity, oblong transversely. 

 From all appearances, the fibula of this animal must have been 

 small and insignificant, there being no mark for its attachment 

 observable on the upper portion of either specimen ; there exists 

 only a doubtful depression on the internal malleolus of the smaller 

 one; it could, however, have had no connection with the tarsus. 

 The articulation of the knee is as simple in the present case as 

 it is most complex in the megalonyx ; but a plenary compensa- 

 tion is found in the lower ankle joint of this animal. At the 

 anterior and inferior extremity of the tibia, between the malleo- 

 lus internus and externus, nearer to the internal, just where the 

 same part in the megalonyx and megatherium projects furthest 

 downwards, there commences a socket 2§ inches long, 2| inches 

 broad, and li inches deep, which receives a corresponding glob- 

 ular or ovoid projection of the anterior superior portion of the 

 astragalus. This cavity descends downwards and backwards to 

 two thirds the thickness of the tibia at this part, when it unites 

 with a transverse semilunar articulating surface, which is slight- 

 ly concave near the external malleolus only; this joins a corre- 

 sponding articulating surface on the astragalus, posterior to the 

 globular or ovoid projection above described, on the outer side of 



