350 Professor Owen 07i 



Comparison of the Modifications of the Osseous Structure of 

 the Megatherium roith that in other known existing and 

 extinct species of the Class Mammalia : Being an Abstract 

 of a Memoir read by Professor Owen to the Royal Society 

 of London. 



Having completed the description of the skeleton of the 

 Megatherium, which was illustrated by an extensive series 

 of accurate and highly finished drawings, the Professor com- 

 pares the modifications of the osseous structure of this gi- 

 gantic extinct animal with that in other known existing and 

 extinct species of the class Mammalia, in the following 

 terms : — 



Osseous Structure of the Megatherium, compared with that in other 

 known existing and extinct species of Mammalia. 



The teeth agree in number, kind, mode of implantation 

 and growth, with those of the Sloth, and their structure is a 

 modification of that peculiar to the Sloth tribe. All the mo- 

 difications of the skull relating to the act of mastication, 

 especially the large and complex malar bone, repeat the 

 peculiarities presented by the existing Sloths. There are 

 the same hemispheric depressions for the hyoid bone in the 

 Megatherium as in the Sloth. In the number of cervical 

 vertebrse the Megatherium, like the two-toed Sloth, agrees 

 with the Mammalia generally. In the accessory articular 

 surfaces aff*orded by the anapophyses and parapophyses of 

 the hinder dorsal and lumbar vertebrae, the Megatherium re- 

 sembles the Ant-eaters {Myrmecophagm) ; but it does not 

 resemble the Armadillos (Das7/pus) in having long metapo- 

 physes, the peculiar development of which, in those loricated 

 Bruta, has a direct relation to the support of their bony 

 dermal armour. In the mesozygapophyses of the middle 

 dorsal vertebrse, the Megatherium is peculiar. In the small 

 extent of the produced and pointed symphysis pubis, it re- 

 sembles the Sloths; and in the junction of both ilium and 

 ischium with the sacrum, it manifests a character common 

 to the Edentate order; but in the expanse and massiveness 

 of the iliac bones, it can only be compared with other extinct 

 members of its own peculiar family of Phyllophagous Edentata. 

 Its habits necessitating a strong and powerful tail, we find 



