96 Professor Owen on the Megatherium. 
affording adequate resistance to the forces acting from and upon 
that great osseous centre. The large processes and capacious 
spinal canal indicate the strength of the muscles which sur 
rounded the tail, and the vast mass of nervous fibre from which 
those muscles derived their energy. The natural co-adaptation 
of the articular surfaces shows that the ordinary inflection of the 
end of the tail was backwards as in a cauda fulciens, not for- 
wards as in a cauda prehensilis. Dr. Lund’s hypothesis, there- 
fore, that the Megatherium was aclimber, and had a prehensile 
tail, is destroyed by the now known structure of that part. 
But viewing, as the Professor conceives, the pelvis of the Me- 
gatherium as being the fixed centre towards which the two legs 
and fore part of the body were drawn in the gigantic leaf-eater’s 
efforts to uprend the tree that bore it sustenance, the colossal prd- 
portion of its hind extremities and tail lose all their anomaly, a0 
appear in just harmony with the robust claviculate and unguicl- 
late fore limbs with which they combine their forces in the Her 
culean labor. 
The Professor then referred to the Mylodon robustus, a smaller 
extinct species of the same natural family of phyllophagus Brita, 
and to the additional arguments derivable from the skeleton ‘of 
that animal in favor of the essential affinity of the Megatherinm 
to the sloths; and the light which the remarkable healed frac: 
tures of the skull of a specimen in the Museum of the College ° 
Surgeons threw upon the habits and mode of life of the specie 
ypothesis of the Degeneration of the ancient Megatherin 
of South America into modern Sloths, erroneous.—F ivally, with 
reference to the hypothesis of the German authors and artists of 
the degeneration of the ancient Megatherioids of South America 
into the modern sloths, the author remarked that the general Ie 
sults of the labors of the anatomists in the restoration of extinct 
species, viewed in relation to their existing representatives of the 
different continents and islands, commonly suggested the idea 
that the races of animals had deteriorated in point of size. Thus 
the palmated Megaceros is contrasted with the fallow deer, and 
the great cave bear with the actual brown bear of Europe. +! 
huge Diprotodon and Nototherium afford a similar contrast with 
the kangaroos of Australia, and the towering Dinornis and the Far 
apteryx with the small Apteryx of New Zealand. But the co#™ 
parative diminutive aboriginal animals of South America, Austl® 
lia, and New Zealand, which are the nearest allies of the gig” 
tic extinct species, respectively characteristic of such tracts of 
and, are specifically distinct, and usually by characters s° Laid 
ei Moreover, as in England, for example, 
water-voles, weasels, foxes, and badgers, are of the sam” 
