GIGANTIC LAND-LIZARD FROM AUSTRALIA. 
555 
class than the shape or substance of any portion of the deciduous appendages of their 
foetus. 
The dermal bones of the Armadillos (Dasypus) have been cited, in like relation to 
guidance as to status in the Mammalian series ; and now, for the first time, we are 
enabled to show that the singular annular arrangement of such ossifications, sustaining 
massive conical cores of corneous weapons, is a repetition of, or, as it were, lias been 
borrowed from, an antecedent cold-blooded, air-breathing class. 
And what are the Mammals that most resemble the scale-clad and bone-clad genera 
in other organic phenomena ? I refer not, now, to the Monotremes and Marsupials ; 
these, by common consent of Systematists, are deposed from the place they hold in 
the Cuvierian system, and are relegated to the lowest position in their class. They 
manifest marked differences amongst themselves, but there is an anatomical character 
common and peculiar to them. It is a cerebral one, in which the great commissure of 
the brain, as it exists in all other and higher Mammals, is represented by a rudiment, 
the connexions and position of which are best expressed by the term “ hippocampal 
commissure.” 
With the Pangolins and Armadillos are associated, also by a cerebral character, the 
Rodents, Insectivores, Bats, and Sloths. In every species of these Orders, as in the 
species of Bruta, the cerebral hemispheres are not extended over any part of the 
cerebellum, and, with few exceptions, are outwardly smooth or unconvolute. At such 
a stage of Mammalian development is it that we find, as in the Lizards and Snakes, 
species becoming torpid in winter, of which Dormice among the Rodentia and Bats 
among insect-eaters are notable instances. In such low Mammals the heart, as in 
Reptilia, retains the faculty of circulating carbonised or black blood. Again, as the 
Pangolin borrows the scales and the Armadillo the scutes of the Reptiles, so the 
Hedgehogs and Porcupines borrow, for their covering, the main part of the feather, 
that, namely, to which it is reduced in the wings of the Cassowary. 
The supernumerary neck-vertebrae and their free or floating ribs is an osteological 
character which has been continued from the Crocodiles to the Sloths ; and the latter 
smooth-brained Mammals show kinship with the antecedent cold-blooded air-breathing 
Vertebrates, by the tenaceous post-mortem irritability of the muscular fibre and the 
long continuance of its contractile response to stimulants. 
Description of the Plates. 
PLATE 64. 
Front view of the ante-penultimate caudal segment, showing the exo- and endo-skeletal 
parts; natural size : Megalama priscci. 
mdccclxxxi. 4 c 
