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cesses of these vertebrae are large, especially in the anterior ones ; but in neither 

 species are the neural spines developed or the haemapophyses present. 



It is in the terrestrial Edentata only that the caudal vertebrie present the fully 

 developed and comphcated condition which has been described in the Mylodon. 

 In all these species, however, the tail is relatively longer than in the Mylodon ; 

 it is even prehensile in the Manis and Myrmecophaga didactyla ; but of the mo- 

 difications of the terminal vertebrse, on which that power depends, there is no 

 trace in the Mylodon. In the relative length of the tail, and in the shape of the 

 hcemal or inferior spines, the Orycterope comes nearest to the Mylodon ; but in 

 no existing quadrupeds, not even in the Kangaroo, is the tail so thick and strong 

 in proportion to its length as in the Mylodon. 



It is, again, amongst its extinct congeners exclusively that we find a close 

 repetition of this part of its organization. The great proportion of the tail of the 

 Megatherium fortunately preserved in the collection of remains of that species 

 transmitted to England by Sir Woodbine Parish, demonstrates a very close cor- 

 respondence in relative size, in structure, and, apparently, also, number of caudal 

 vertebrae, with the Mylodon. 



The transverse processes of the analogous vertebrae are stronger, and trihedral, 

 instead of being compressed ; the superior spinous processes were developed 

 along a greater extent of the tail ; the form and relative size of the inferior spines 

 and the mode of articulation of the haemapophyses are closely similar. These 

 vertebral elements remain separate from each other in the first caudal vertebrae, 

 in the Megatherium as in the Mylodon ; in the rest they are united to form the 

 chevron-bone, developing a long and strong spine from their point of union. 



Description of the Bones of the Anterior Extremity. 

 This powerful member does not exceed the hind-limb in length ; it consists in 

 the skeleton of a scapula, clavicle, brachium, antibrachial bones and manus, and 

 includes every perfection of structure manifested in the Mammahan class, save 

 the opposable thumb. 



Scapula. — ^The scapula* is a large inequilateral four-sided plate of bone ; the 

 longest side, which is convex, forming the base ; the shortest, which is concave, 

 supporting the articular cavities for the humerus and clavicle : the upper and 



* Plate I. 



