HISTORY OF THE EDENTATA 611 



In most existing genera, the carapace is in three parts, an an- 

 terior and posterior buckler, in which the plates are immovably 

 fixed together by their edges, and between a varying number of 

 transverse, overlapping bands, from 3 to 13, which permit 

 sufficient flexibility of the body. The tail-sheath is made up 

 of a series of rings. One genus (Tolypeutes) has the power of 

 rolling itself into a ball, the head-shield exactly closing the 

 anterior notch of the carapace and the tail-sheath filling the 

 posterior notch. The animal is thus perfectly protected against 

 attack and does not seek refuge by digging, as other armadillos 

 do and with astonishing rapidity. In the little Pichiciago 

 (Chlamydophorus) the dermal ossifications are very thin and 

 the carapace is composed of twenty transverse bands of horny 

 plates, without bucklers ; the rump is covered with a broad 

 and heavy shield of bone, overlaid with thin plates of horn, 

 which is attached to the hip-bones and notched below for the 

 short tail. In certain rare and little known genera there is a 

 greater development of hair ; in one (Praopus) the whole 

 carapace is covered with a dense coat of hair, and in another 

 (Scleropleura) the middle of the back has only a hairy skin and 

 the carapace is restricted to the sides. 



The teeth vary in number and size in the different genera ; 

 in some {e.g. Dasypus) there is one upper incisor on each side ; 

 the teeth are all simple and of nearly cylindrical form. The 

 skull is low and flattened, with long tapering snout and orbits 

 widely open behind ; the zygomatic arches are uninterrupted. 

 Most of the vertebrae of the neck are fused into a single piece ; 

 in the lumbar and posterior dorsal regions there are not only the 

 usual highly intricate articulations between the vertebrae, but 

 also high processes on each side for the support of the carapace. 

 The fully ossified sternal ribs have movable joints with the 

 breast-bone, but not the double articulations found in the ant- 

 eaters and tground-sloths. The shoulder-blade has a very 

 long acromion, which does not form a bony loop with the cora- 

 coid, and the clavicles are complete. The anterior element 



