164 AMERICAN EDENTATES CHAP. 
sentatives have as yet been discovered which can be referred to 
the Anteater, Armadillo, or Sloth type with certainty.! 
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 XENARTHRA 
has been suggested for the American Edentates with “abnormal ” 
vertebral articulations; the corresponding NoMARTHRA 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 
é are certain important resemblances be- 
eS tween the living forms. In both, retia 
be mirabilia are developed in the tail (in 
a7 \* spite of its reduction in the Sloths) and 
in the hmbs. 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- 
Fre. 90-— Right scapula and clavi- acter they share with the Armadillos 
cle of Two-toed Sloth (Choloepus : - c 
hofmanni). x1. a, Acro. and with the Aard Vark; Manis hav- 
mion; 4, prescapular fossa ; ing a non-deciduate placenta which is, 
ce, coracoid ; c/, clavicle; esf, — © 5 R x 
coraco-scapular foramen; ge, like that of the Carnivora, zonary in 
glenoid cavity ; pf, postscapular A ; eats mE 
fossa. (From Flower’s Osteology,.) 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? 
‘ A rather problematical Armadillo, Necrodasypus, has been recorded from 
French strata. It consists of a few scutes only. 
? Proc. Zool. Soc. 1882, p. 358. 
