SUCCESSION OP THE TEETH IN THE DASYURIDiE. 
459 
teeth. Then, with merely the slight modification of the loss of the first four pre¬ 
maxillary teeth, we get /3, the dentition of Dasypus ; next, by the suppression of the 
last premaxillary tooth as well, we obtain y, that of Xenurus, Tolypeutes, and 
Chlamyclophorus. Then, on the one hand, a simple increaseof the number of the 
maxillary teeth to 20 or more results in S, the dentition of Priodon, and, on the other, 
a similar decrease to 5 in that of Bradypus and its allies, both recent and fossil (e). 
This reduction is then carried out to its extreme in Myrmecophaga and Manis (£), 
both entirely toothless. Finally, y based on y, with the superaddition of a nearly 
complete set of milk-teeth, gives us the remarkable and unique double dentition of 
the genus Tatusia. 
Should this view of the derivation of the Edentata be correct, it is evident that 
their line of development should have a name corresponding to the useful evolutionary 
terms suggested by Professor HuxLEYf for the great Mammalian groups, and since 
almost universally used. I would, therefore, altogether remove the Edentates from 
the “ Eutheria ” and call them the “ Paratheria,’’ to indicate their position by the side 
of, bub separate from, the other Mammals. 
One genus of Edentates has not been mentioned, namely Orycteropus, with its 
extraordinary canaliculated compound teeth, wholly unique among Mammals, and 
only comparable to those of certain Fish. I can, however, at present make no sugges¬ 
tion as to the origin or evolution of these teeth, there being as yet no evidence bearing 
upon them in any way. 
Putting now together all the diagrams above worked out, we obtain the general 
genealogical Table (Plate 28), in which the three great lines of development are shown, 
viz., the main Proto-meta-eutherian stem, I. to XIII., at the bottom of which all the 
modern Placentals stand; I.-a to I.-y, the Edentate or Paratherian line; and I. to IV., 
and from IV. to 1V.-A-, that of the Marsupials. 
The influence that these theories, if correct, will exercise on tooth-notation is a 
matter of detail which will require proper working out in each group; but it is 
evident that such generalisations as that missing incisors are always gone from the 
posterior and missing premolars from the anterior ends of the series are quite 
untenable, and that every group must have the homologies of its teeth worked out 
for itself, and not merely put down under the influence of any such general rule. 
This influence has even caused such eccentricities as the numbering of the premolars 
from behind forwards, a proceeding which woidd, for example, result in the two 
premolars of Dcisyurus being called (from before backwards) pm 3 and pm 1 , instead 
of, as they have above been shown to be, pm 1 and pm 3 respectively. 
Having now put forward the views gained by my own examination of specimens, 
there remains to be noticed the other published work on the subject. The numerous 
contributions to the history of teeth made by Sir Pichard Owen during the last 50 
* Or, perhaps, rattier a retention of the numerous teeth no doubt possessed by the earliest Prototheria. 
t ‘ Zooh Soc. Proc.,’ 1880, p. 653 et seq . 
3 N 2 
