FOSSIL MAMMALIA. 85 



of the chest. The state of the fossil did not afford further information as to the 

 condition of this part of the vertebral column, but the parts which have been pre- 

 served are precisely those from which the most interesting inferences as to the 

 affinities and habits of the extinct quadruped can be deduced. 



Whether the Megatherium be most nearly allied to the tribes of the Sloth or 

 Armadillo has been a question under recent discussion, and, as a corollary of this 

 problem, whether its habits were those of a scansorial or of a fossorial quadruped. 

 For, strange as it may appear at first sight, there have not been wanting argu- 

 ments, and those urged by an anatomist to whom we owe much novel and interest- 

 ing information respecting the extinct Edentata, in support of the belief that the 

 Megatherium, gigantic and ponderous as must have been its frame, actually 

 climbed trees like a Sloth, and had claws and feet organised for prehensile actions, 

 and not in accordance with that type by which they are usually adapted for dig- 

 ging up the soil.* 



Now, in whatever degree the Megatherium may be involved in this question, the 

 smaller Megatherioid species at present under consideration must be at least 

 equally implicated in it. In the adaptation of the frame of a mammiferous qua- 

 druped for especial and peculiar actions and modes of life, such as for climbing 

 and living in trees, or for burrowing and seeking concealment in the earth, not 

 only the immediate instruments, as the feet, are modified, but the whole of the 

 osseous and muscular fabric is more or less impressed with corresponding adap- 

 tations, whilst at the same time these special adjustments are invariably subordi- 

 nated to the type of organization which characterizes the group. 



The type of the order Bruta or Edentata is well-marked ; one or more claws 

 of unusual length and strength, characterize the fore-feet and sometimes the hind- 

 feet in every genus, and the term ' Macronykia' would more aptly designate them 

 than the term which Cuvier substituted for the good old Linnsean appellation. The 

 uniform absence of true roots to the teeth, where these are present, is another 

 general character ; the skeleton exhibits many well-marked peculiarities common 

 to the whole order ; while at the same time it is modified in various modes and 

 degrees in accordance with the peculiar habits and exigencies of the species. 



One of the regions of the skeleton which manifests adaptive modifications of 

 this kind in the most remarkable degree is the cervical division of the vertebral 

 column. In one edentate species it is lengthened out by two additional vertebra 

 more than in any other mammal ; in another it is reduced by anchylosis to as great 

 an extent below the regular number of moveable pieces : and these, the two most 

 opposite conditions of the cervical vertebras which are to be met with in the 

 mammiferous class are related to equally diverse and opposite habits of life. 



* Lund, Videnskabernes Selskabs, Natur : og Mathem. Afhandlinger, Kiobenhavn, vol. viii. 



