XATl'RAL HISTORY OF THK PRTIIKVAL WORLD. 



43 



Ih'. IJiicklaiicl puiiits out tliat the s.icral bone is 

 united to llie pelvi:^ in a very singular manner, evi- 

 dently witli tlie olject of securing tiie greatest possible 

 amount of strength, while its processes indicate tliat 

 tlie muscles regulating the movement of the tail were 

 of great power. 



The tail was long, and composed of vertebrpe of 

 enormous nurgnitude ; the body of the largest measur- 

 ing not less than seven inches in diameter, while the 

 distance liorizontilly between the extremities of the 

 two transverse processes was twenty inches. Include 

 the thickness of the muscles and tendons, and of the 

 shelly integument, and you cannot eslimate the dia- 

 meter of the tail at its root at less than tivo feet ; 

 while its circumference, supposing it to be nearly cir- 

 cular, like the tail of the armadillo, would be about 

 si.N feet, or twice llie size of a well-grown man. These 

 vast dimensions, observes our authority, are not larger, 

 in proportion to the adjacent parts of the body, than 

 tliose of the armadillo; and as this aiunial makes use 

 of its tail as an auxiliary in supporting the weight of 

 its body and armour, we may reasonably infer that the 

 ML-gatherium employed its huge caudal extremity in a 

 similar manner.* The large infeiior spines, or addi- 

 tional chevron bones, attached to the caudal vertebrw, 

 by increasing the strength of the tail, would render 

 it more usefcd in this important rest. But the tail 

 was also- [irobably employed as a powerful defensive 

 weapon, like that of the crocodiles and pangolins. 



The ribs of the Megatherium are at once thicker, 

 sliorter, and more substantial than those of the rhino- 

 ceros or elephant ; and in some of them the convex 

 upper surfaces exhil>it a rugose and flattened condi- 

 tion, sliowing the poiuls where the weight of the bony 

 cuirass chiefly rested. 



The satjmla, or shoulder-bone, is unlike that of any 

 other family, except the Sloth, and displays in the 

 acromion " contrivances for strength, peculiar to itself 

 and them, in its mode of articulation with the collar- 

 bone ; it also exhibits unusual provisions for the support 

 of the most powevfid muscles for the movement of 

 the arm." 



The clavicle, or collar-boue, is strong, and incur- 

 vated nearly as in man. From the presence of this 

 bone, which is wanting in the elephant, the rhinoceros, 

 and all the large Ituniinautia, we conclude that the 

 fore-leg fcdfilled some other function thau that of a 

 mere locomotive organ. This clavicle would alTord a 

 steady and permanent position to the socket, or glenoid 

 cavity of the scapula, and so permit the ariimal's fore- 

 leg, like the human arm, to move freely in a rotatory 

 mauner. 



In these circumstances we find, snys Dr. Buckland, 

 whose admirable description of the Jlegatherium we 

 have closely followed — 1st, That a free rotatory power 

 of the fore-leg was auxiliary to its ofiiee as an instru- 

 ment to be continually employed in digging fol;d out 

 of the ground ; 2nd, That this act of perpetual digging 

 in search of stationary objects like roots, needed but 



• The elepliant^s tail i.-^ remiirkal»ly liglit and -slender, being 

 cliieHy used to brush otT insects; tliat of the Iiippnpotanius, 

 being intended to act like a rudder when tlie animal is swim- 

 ming, is only a few inches long, and vertically flattened. 



little locomotive power; and oid, That the compara- 

 tively slight support rendered to the weight of tlie 

 huge armour-plated body by the fore-leg, was abun- 

 dantly compensated by the extraordinary, the almost 

 gigantic strength, of the haunches and hind legs. 



In the elephant the excessive weight of the animal's 

 head, proboscis, and tusks require a short, thick neck, 

 and a proportionate development and solidity in the 

 fore legs, which are consequently built up, so to speak, 

 on a stronger and bolder scale than the posterior ex- 

 tremities ; but with the Jlegatherium we find the relative 

 proportions reversed : a small head is accompanied by 

 a long neck, and the anterior portions of its body are 

 but slightly weighted in comparison with its abdominal 

 and posterior regions. So exquisite is the foresight, 

 so ingenious the contrivance, which we discover mani- 

 fested in the smallest details- of animal organization 1 

 Every want is met as it arises ; nowhere does any 

 .slovenliness or rudeness prevail, but an abundant pro- 

 vision is made for the comfort, well-being, and com- 

 pleteness of every creature. 



To secure strength and f icilitate motion for the fore- 

 legs of the Megatherium there exists, then, a peculiar 

 adaptation of the shoulder-blade and collar-bone. But 

 this strength is not merely intended to sustain the 

 weight of the body, nor is this motion designed to be 

 progressive. The humerus articulates with the scaprda 

 by a round head, which admits of unrestrained motion 

 in various directions. It is small at its upper and 

 middle part, but at its lower end attains extraordinary 

 breadth, owing to an enormous expansion of the crests 

 which rise from the condyles, to give origin to the 

 muscles for the movement of the fore-foot and toes : 

 just such an expansion, we must observe, as is found 

 in the lower part of the humerus of the ant-eater, 

 which employs its fore-feet in digging up the solid 

 hills of the termite ants. The ulna is singularly broad 

 and powerful at its upper extremity, aft'ording a large 

 space for the origin of the muscles which regulate the 

 movement of the foot. 



The entire fore-foot must have been about thirty- 

 ,six inches long and upwards of twelve inches wide, 

 forming a most efficient instrument for moving the 

 earth from that depth within which succulent roots 

 are generally most plentiful. This great length of the 

 fore-foot, when resting upon the ground, however 

 inconsistent with rapid progressive motion, must have 

 been of the highest value in enabling one fore-leg, in 

 conjimction with the hind-legs and tail, to support the 

 whole pressure of the Megatherium's body, while the 

 other fore-leg was exclusively employed in the operation 

 of digging up food. 



The fore-foot of the armadillo {Dasypus peba), and 

 of the Chlamyphorus, is similaily adapted for digging 

 purposes; and in each may be observed an unusual 

 enlargement and elongation of the extreme bones of 

 the toes for the support of long massive claws. Such, 

 too, was the case with the Megatherium ; the bones 

 supporting the claws were composed partly of an axis, 

 or pointed core, which filled the internal cavity of the 

 horny claw, and partly of a bony sheath foiniing a 

 strong case to receive arid support its root. These 

 claws were placed obliquely to the ground, like the 



