Geological Society. 519 



of the Mole ; but it is the fore foot only of this animal that can be com- 

 pared in the compressed figure of the metacarj:)als and proximal and 

 middle phalanges with the singular hind-foot of the Glyptodon. The 

 hind foot of the Mole resembles in the lengthened metatarsal and jjlia- 

 langeal bones that of the existing Armadillos, and the generality of 

 quadrupeds. The true structure of the hind foot of the Megatherium 

 is not known, but in the terminal phalanges it diflfers most widely 

 from those of the Glj^ptodon. In the former, the compressed length- 

 ened shape is as extreme in the claw-bones as, in the latter, is the 

 depressed, shortened figure. In the Glyptodon, the hind foot, like 

 the fore, appears to be expressly modified to form a base to a column 

 destined to support an enormous superincumbent weight ; while in 

 the Megatherium the toes were free to be developed into long and 

 compressed claws, such as form the compensating weapons of de- 

 fence of the hair-clad Sloths and Ant-eaters. The ungueal phalanges 

 of the Armadillos, in their shorter, broader, and flatter form, make a 

 much nearer approach to those of the Glyptodon ; and it may be 

 readily admitted that the hind foot of the Glyptodon is an extreme 

 modification of the same general plan of structure as that on which 

 the foot of the Armadillo is constructed ; but if the diiferences in 

 the tarsal bones (described in the paper) exceed those which are 

 traceable between one species of Armadillo and another, a fortiori, the 

 antero-posterior compression of the metatarsals and phalanges, and 

 the total suppression in those of the ginglymoid trochlear articula- 

 tions are indicative of a difterence of general habits, as great as is 

 usually observed in animals of distinct but nearly-allied genera. Thus 

 both the dental modifications and the locomotive organs prove that 

 the Glyptodon cannot be called an Armadillo without making use of 

 an exaggerated expression ; still less can it be considered a species 

 of Megatherium ; but it offers the type of a distinct genus, which is 

 much more nearly allied to the Dasypodoid than to the Megatherioid 

 famiUes of Edentata. For this genus Mr. Owen had proposed a name 

 indicative of its dental peculiarities, and, as the present species agreed 

 with the Armadillos in its dermal armour, he preferred the name of 

 Glyptodon clavipea, in relation to the peculiar modification of the 

 foot. 



Mr. Owen then showed that the portions of tessellated armour 

 described and figured by Weiss are identical in structure with those 

 brought to England by Sir Woodbine Parish, and that the bones 

 which were found with tlie armour in both cases belonged to animals 

 specifically identical. He next entered upon the inquiry, Had the 

 Megatherium a l)ony armour .'' and he concluded from a comparison of 

 its skeleton with that of the Armadillos, that it had not. In the jjclvis 

 of tlie Armadillo there are twelve sacral vertebra? anchylosed to- 

 gether, and the spines of tlie vertebnc arc greatly developed antero- 

 jjosteriorly, forming a continuous vertical ridge of bone, bearing im- 

 mediately the .'iuijerincumbent weight. In tlie Mcgathere the sacral 

 vertebric are only four in iiuinl)er, and are not ancliyloscd, and the 

 spinous ])rocesses are comparatively small, not locked together, as in 

 the Armadillos, but separated by intervals as in the Sloths. In the 



