164 



AMERICAN EDENTATES 



CHAP. 



sentatives have as yet been discovered which can be referred to 

 the Anteater, Armadillo, or Sloth type with certainty. 1 



Of these American forms, which will be treated of first, the 

 Armadillos are further apart from either Sloths or Anteaters 

 than the last two are from each other. The name XENARTHKA 

 has been suggested for the American Edentates with " abnormal " 

 vertebral articulations ; the corresponding NOMAETHRA includes 

 the Old-World forms. 



Between the Sloths and Anteaters the extinct Megatherium 

 and some of its allies are to a certain 

 extent intermediate. But it may be 

 pointed out in the first place that there 

 are certain important resemblances be- 

 tween the living forms. In both, retia 

 mirabilia are developed in the tail (in 

 spite of its reduction in the Sloths) and 

 in the limbs. But, as is well known, 

 retia are also found in other mammals 

 far removed in the series from these 

 under consideration. The reproductive 

 organs generally are very similar, and 

 they have both a dome -shaped and 

 deciduate placenta. The latter char- 



FIG 90 '.-RigM scapula and clavi- act er they share with the Armadillos 

 cte or Two-todd Biota (CAogogHM . J 



a, Aero- and with the Aard Vark ; Manis hav- 



in S a * on - d <*iduate Placenta which is, 

 like that of the Carnivora, zonary in 

 form - The Edentates, at any rate the 

 American forms, have a double vena 

 cava posterior and no azygos vein. This condition is also met 

 with among Whales. 



Osteologically the Sloths and Anteaters are united by the 

 fact that the coracoid becomes fused with the coracoid border 

 of the scapula, thus forming a foramen ; the importance of this 

 character is, however, discounted by its occurrence in three 

 genera of Cebidae. 



The above facts embody the views of Sir William Flower. 2 



1 A rather problematical Armadillo, Necrodasypus, has been recorded from 

 French strata. It consists of a few scutes only. 



2 Proc. Zool. Soc. 1882, p. 358. 



x i 



coraco- scapular foramen 



