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1891.] Geology and Paleontology. 1001 
Among the important discoveries are the numerous ? Marsupialia. 
Several of these belong to the genera allied to the Plagiaulacide 
already described by M. Ameghino. The author has discovered a 
fact long since (AMERICAN NATURALIST, 1884) pointed out by myself,— 
viz., that the cutting inferior molar of the Plagiaulacide is not homol- 
ogous with the cutting tooth of the mandible in the Marsupialia Dipro- 
todonta, but is one position posterior to it. I regarded it asthe P. m. 
i. (iv.), but Ameghino, following Thomas’s nomenclature, regards it as 
the m. i. Garzonia g. n., Epanorthus, and Microbiotherium are made 
types of new families with apparent reason. So is Abderites, but no 
sufficient ground appears to be given inits case. Three new genera and 
seven new species are referred to the existing family Thylacynidz, thus 
bringing to light the lost relatives of the Tasmanian wolf-opossum. 
An affinity between these animals and the Creodonta of the same age 
is insisted on. 
In a previous essay Ameghino shows that Propalzehoplophorus has , 
distinct vertebre, and represents therefore a family entirely distinct 
from the Glyptodontidz. Cochlops belongs to the same family. He 
adds much to our knowledge of Peltephilus, which M. Mercerat 
declares to be identical with Cochlops. Family names appear to be 
rather carelessly used among the Glires ; there are too many of them. 
mong Litopterna, Mesorhinus Amegh. is made the type of a new family, 
which has the external nares placed more anteriorly than in the Macrau- 
cheniidæ ; he includes in it the genera Mesorhinus, Oxyodontotherium, 
Ccelosoma, Theosodon, and the new Pseudoccelosoma. Several impor- 
tant points in the structure of Homalodontotherium are added ; among 
the rest, that it has an ungrooved astragalar trochlea. A new species is 
described, and a new genus (Diorotherium) is added to the family. 
Eleven new species are added to the Proterotheriide. Astropother- 
iidæ are still referred to the Amblypoda Taligrada, and a new genus 
(As tapudan] is added. Many striking novelties are added to the 
Toxodontia, 
This contribution increases our interest in this wonderful fauna, and 
leads to the hope that we shall soon see the illustrations of some of the 
forms already promised by M. Ameghino.—E. D. Cope. 


