Mammalia. Marsupialia. 51 



in all Dasypodidae and Cholaepus; are small and rudimentary in 

 Myrmecophagida?, absent in Manis, and so short as not to reach the 

 sternum in the Sloth. The Humerus is generally well developed, 

 short and broad in the Armadillo, long in the Sloth, varying, as also 

 do the Antibrachial bones, with the burrowing or climbing habits of 

 the different species : it is generally perforated above the inner 

 condyle;]:. The Zflna is generally longer (ex. Manis) than the Eadius, 

 often much stronger {^.y. Armadillo), and usually possessed of a well- 

 developed Olecranon. In all In-Enamellata the Radius is free, and 

 rotates on the Ulna : in the Sloth these bones are so articulated as 

 to allow of pronation and supination. The Metacarpal hones in the 

 Sloth are united together posteriorly, and also with the front row of 

 Phalangeal bones. The Ungual Phalanx of the Ant Eater is charac- 

 terised by being split at the extremity by a longitudinal fissure, 

 commencing at the upper part of the base {cf. Perameles, Marsu- 

 pialia). 



Pelvic Arch and Appendages. The Ischia are largely developed in 

 all except the Sloths: and except in Orycteropus unite with the 

 vertebral column. The Ilia are generally firmly and extensively 

 united with the Sacrum. The Pules are always slender, and form 

 but a narrow ossified symphysis. The large Pelvis, the union of 

 the Ischia with the Sacrum, and the speedy osseous confluence of 

 the several pelvic elements are common characteristics of the spinal 

 column of the In-Enamellata. The Armadillos are marked off from 

 the Sloth and Ant Eaters by having a third trochanter to the Eemur^ 

 and the proximal and distal extremities of the Tilia and Filula 

 conate. In both Sloth and Ant Eaters, the Tibia and Fibula are dis- 

 tinct (in the former they are oppositely bent, leaving a wide inter- 

 osseous space), and both fore and hind feet have an inclination 

 inwards, owing in the latter case to the downward projection of 

 the outer Malleolus, which fits like a pivot into a socket in the 

 Astragalus. 



XIY. MAESUPIiLIA. 



The Skull is generally more depressed and flattened than in the 

 Placental Mammalia ; and is remarkable for the small proportion 

 which is devoted to the protection of the brain, and for the great 

 expansion of the nasal cavity immediately anterior to the cranial 

 cavity : it usually converges ^gradually towards the anterior ex- 



X Except Manis. 



