726 The American Naturalist. [August, 
The most important results achieved by M. Ameghino are as follows : 
First, the discovery and definition of numerous marsupialoid or multi- 
tuberculate forms from the Eocene of Patagonia; second, the discovery 
of Creodonta in the same region and horizon ; third, the discovery of 
Edentata with enamel bands on the teeth ; fourth, the definition of the 
siborder Litopterna, and discovery of new types; fifth, the completed 
definition of the order Toxodontia. To these points may be added 
as only second to them in importance the discovery of Eocene forms 
of Edentata with superior incisor teeth, and the great additions to 
the number of forms of Edentata, Glires, and Toxodontia. i 
The marsupialoid forms are of great interest. Abderites resembles 
the Plagiaulacidz, while in Epanorthus we have a type which shows 
how the singular cutting premolar of this type or that of the Marsupi- 
alia Diprotodonta may have been derived from a primitive tuberculo- 
sectorial tooth. The occurrence of these forms in the Eocene of 
Patagonia is a fact of great significance, and M. Ameghino regards 
them as true Marsupialia, and the ancestors of the Diprotodonta of 
Australia. ; 
The Creodonta mostly repose on the evidence of imperfect material. 
Some of them have a simple dentition, and much remains before their 
true affinities can be determined. 
The suborder Litopterna deserves more detailed notice, and we give 
it in another place in the NATURALIST. It is a most interesting modi- 
fication of the Condylarthra, showing variations in dental and foot 
structure parallel with those seen in the Perissodactyla, with which I. 
think M. Ameghino wrongly combines them. 
The light thrown on the structure of the Toxodontia is most impor- 
tant. The structure of the posterior feet has been hitherto but partially 
known, and that of the fore feet entirely unknown. M. Ameghino 
shows that the former are taxeopodous, and the latter amblypodous, 
proving conclusively the claim of the Toxodontia to be regarded as a 
distinct order of ungulate Mammalia. An important feature of this 
book is the number of new genera allied to Mesotherium which are 
described and figured. 
The great number of Glires described is remarkable. It is inter- 
esting to observe that they correspond with existing forms of South 
America, the Chinchillide and Caviide being most numerous, even in 
Eocene times, while the Leporidz are very few, and present only in 
the latest beds. 
As a general result of M. Ameghino’s work it is now possible to 
announce the following conclusions: The extinct Mammalia may be 


