6 PATAGONIAN EXPEDITIONS: PAL/EONTOLOGY. 



maxillary, and in position it may be at the anterior or the posterior end, 

 or in the middle of the arch. The arch itself is always complete, never 

 rudimentary, though in the Gravigrada the jugal is usually loosely attached 

 and has been lost from most of the specimens. 



5. The neck has never more or less than seven vertebra, though in all 

 of the armadillos and glyptodonts the apparent number is much reduced 

 by coossification. In the same two groups the trunk is short and the 

 number of trunk-vertebrae small and in the glyptodonts these vertebras 

 are coossified into long "tubes," one thoracic, the other lumbo-sacral. 

 In the Gravigrada, on the contrary, the trunk is very long and the trunk- 

 vertebrae numerous. In both armadillos and ground-sloths the lumbar 

 and posterior thoracic vertebrae have very complex accessory zygapoph- 

 yses, which in the former are as fully developed as at the present time, 

 but in the latter are somewhat less so than they became at a later period. 

 The sacrum may be long (Dasypoda, Glyptodontia) or short (Gravigrada) 

 but always articulates with both ilia and ischia. The tail is sometimes of 

 moderate length and sometimes very long, but is always heavy and 

 always has a complete series of chevron-bones. 



6. The limbs and feet differ greatly in the three orders and have com- 

 paratively little in common. The scapula is broad and has an ex- 

 tremely prominent spine and acromion ; the coracoid is very large in the 

 ground-sloths, reduced in the glyptodonts and armadillos, except Pelte- 

 pliiliis. In all three orders the humerus has a similar general appearance, 

 having small tuberosities, extremely prominent deltoid and supinator 

 ridges and internal epicondyle, while the foramen is large. Ulna and 

 radius are separate and, except in the ground-sloths, the former has a very 

 large olecranon. All the carpals are free, but no genus has been found 

 which has the centrale. The manus is pentadactyl and plantigrade, 

 though it is not improbable that the Gravigrada had already begun to rest 

 the ulnar edge of the hand upon the ground ; the metacarpals are free 

 and, except in one species of armadillo, none of the phalanges are coossi- 

 fied. The unguals are generally longer and more pointed than in the pes. 



The pelvis [differs much in the three groups, but the ischia are always 

 extensively connected with the sacrum. The femur is long and has prom- 

 inent trochanters and in some of the armadillos the great trochanter 

 reaches extraordinary proportions. Tibia and fibula are free in the Gravi- 

 grada, coalesced at both ends in the glyptodonts and armadillos. The 



