204 STUDIES IN THE EVOLUTION OF ANIMALS 



some monstrous form, without plate-armour, may have occurred all 

 of a sudden, just as hairless animals have suddenly appeared. 



In Chlamydophorus we have probably a curious illustration of a 

 transition form. The calcareous shield has disappeared, and hair 

 has grown in its stead ; and over this the horny covering of the 

 bony carapace still remains. By getting rid of the latter also we 

 would have the finished hairy mammal, with pigment-rosettes on 

 its hair to show its connection with carapaced animals. 



But the reader might say this tiny Armadillo has no spots on its 

 hairy coat, although it would seem to have recently lost its bony 

 shield. No one would expect the law of spotting to be so un- 

 changeable as not to admit of any deviation. Indeed, in some 

 forms of Lynx we have the back unspotted, while the abdomen is 

 spotted and the short tail ringed. 



To return to our question then What could have caused the 

 gradual disappearance of armour, such as we know to have existed 

 in many extinct mammals, which at one time appear to have been 

 very numerous ? It is stated x that ' the habitat of the Armadillos 

 extended from Mexico and Texas to Patagonia, and during the 

 Tertiary Period was inhabited by the Glyptodons gigantic 

 Armadillos whose remains are found abundantly in the bone caves 

 of Brazil.' 



It is evident to me that these armoured mammals lost their 

 armour gradually. Some had very thick bony plates, others thin ; 

 some had their scutes commissured, others had them separate ; 

 in others, finally, there were only vestiges of bony scutes. 



This is what Palaeontologists say, 2 under the heading of Glyp- 

 todons : ' Carapace has no movable bands, so that the animal 

 could not roll itself up ; ... the carapace usually has its com- 



1 Encyclopedia Britannica, vol. ii., pth edition. 



2 Manual of Paleontology, Nicholson and Lydekker, vol. ii. p. 1292. 



