GENERAL CHARACTERS 177 
remarkable exceptions of Tatusta and Orycteropus, monophyodont ; 
they are never rooted, but have persistent pulps; except in some 
fossil forms, they are always deficient in one of the constituents 
which enter into the formation of the complete mammalian 
tooth, the enamel; and, at least among living forms, are never 
present either in the upper or lower jaw in the fore part of 
the mouth, the situation occupied by the incisors of other 
mammals.1 
The peculiar nature of the dentition in the aberrant Orycteropus 
will be noticed under the heading of that genus. As a rule, the 
coracoid process of the scapula of the Edentates is more developed 
than in other Eutheria. 
The degree of development of the brain varies considerably in 
the different families, the 
hemispheres being in some 
cases almost or quite smooth 
(Fig. 57), with a small corpus 
callosum, and large anterior 
commissure ; while in other 
instances the hemispheres 
are convoluted, and the 
corpus callosum is larger. 
There is so great a differ- 
ence in structure and habits 
between some of the existing 
animals assigned tothis order 
Fic. 57.—Upper surface of the brain of the Broad- 
7 banded Armadillo (Xenurus wnicinctus). The large 
that, beyond the negative olfactory lobes are seen at the anterior extremity 
characters just mentioned, (left of figure); the hemispheres have only three 
there seems little to connect sulci. (From Garrod, Proc. Zool. Soc. 1878, p. 230.) 
them. The Sloths and Anteaters, for instance, in mode of life, 
general conformation of limbs, structure of digestive organs, etc., 
appear at first sight almost as widely separated as any mammals. 
Paleontology has, however, thrown great light upon their relations, 
and proved their real affinities. Perfectly intermediate forms have 
been discovered in the great Ground Sloths of America, which have 
the dentition and general form of the head of the Sloths, combined with 
the limbs and trunk of the Anteaters. It is, indeed, highly probable 
that the existing members of this order are very much differentiated 
representatives of a large group, the greater number of which are 
now extinct, and have become so without ever attaining a high 
grade of organisation. The great diversity of structure in the 
existing families, the high degree of specialisation to which many 
have attained, the paucity of species and even of individuals, their 
1 In some few Armadillos the suture between the premaxilla and maxilla 
passes behind the first upper tooth ; but in all other known members of the order 
all the teeth are implanted in the maxilla. 
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