THE WADSWOETH GALLERY. 



19 



The head'' of the Megatherium 

 is remarkalle for its relatively 

 small size, for the extraordinary 

 depth of the lower jaw, and for 

 the great size of the zygomatio 

 processes. The length of the skull 

 is 31 inches : 3 inches less than 

 that of the Asiatic Elephant. 

 The formation of the muzzle in- 

 dicates the possession of a short 

 proboscis. The dental formula is 

 |-f — 18. The teeth are 

 prismatic and slightly 

 curved, and measure from 

 eiglit to ten inches in 

 Iciugth, and between two 

 and three inclics in 

 breadth.^ In composition, 

 a central axis of vascular 

 dentine is inclosed by a 

 wall of unvascular dentine, and this by one of cement. 



The spinal column consists of seven cervical, sixteen dorsal, three lumbar, 

 five sacral and eighteen caudal verte'^rae, and nnasures fifteen feet in length, 

 or three feet more than the Elephant. The circumference of the skeleton, at 

 the eighth rib, is eleven feet. 



In no respect does the Megatherium differ more strikingly from existing 

 quadrupeds of correspon ling bulk, than in the va^t proportions of its an- 

 terior extremities. Its clavicle, fifteen inches long, is the longest known. 

 The foreleg bespeaks enormous strength ; with the foot, it is seven feet and 

 four inches in length.* 



The posterior extremities are shorter than the anterior. The pelvis is tho 

 largest bone in any land animal, living or extinct : it is upwards of five 

 feet broad. The rugged ilium and spinal crest show that it was the centre of 

 muscular bundles of enormous power, which diver jed to act upon the trunk, 

 the tail and the hindleg-. These muscles, judging from the size of the spinal 

 cord, which in this region is four inche? in diameter, m ist have been cha- 

 racterized ly the extreme energy of their vital contractibility. The acetabu- 

 lum is excavated in a very exceptional manner, its concavity facing directly 

 downward. This gave increased strength for sustaining vertical pressure at 

 the expense of rapid motion. 



The hin llegs appear more like columns for support than org.ins for loco- 

 motion, and, with the hin ./feet, are models of massive organic masonry.^ The 

 heel-bone alone has the extraordinary length of seventeen inches, and a 

 circunjference of twenty-eifht inehes. The monster walke I, like the Ant- 

 eater, on the outside edge of its foot, on a marginal hoof-like callosit}-. The 

 mid lie toe of* th.- hindfoot, and likewise the seeon 1, third and fourth digits 

 of the forefoot, were armed with powerful claws. The magnitude of the tail 

 fills the observer with wanier : when clothed w th flesh, it must have l)cen 

 more than six feet aroun I at the greater end. Witli the hindlcgs, it formed 

 a tripol upon which the animal rested when obtaining its fool. 



It would be interesting to know something of the daily life of nn animal 

 whose colossal size was u!iited to such strange anatomy. As the brain of 

 the Megatherium was less I y nearly one-lialf than thit of the Elephant, wc 

 infer that he was a creature of fewer instincts. Nevertheless his cotemporary 

 quadrupeds must have acknowledged him as the head of the Animal King- 



