Prof. K. A. von Zittel—On the Mammiia. 403 
genera on both continents are placed opposite each other, and those 
from the English Great Oolite are indicated by (G. O.) and those 
from the Purbeck by (P.). 
ENGLAND. NortH. AMERICA, 
Amphilestes (G. O.) Priacodon. 
Triconodon (P.) Triconodon. 
Phascolotherium (G. O.) 
Spalacotherzum (P.) Tinodon. 
Dicrocynodon. 
Docodon. 
Linnacodon. 
Amphitherium (G. O.) 
feramus (P.) 
Amblotherium (P.) Paurodon. 
Achyrodon. Laodon. 
Dryolestes. 
Asthenodon. 
Curtodon (P.) 
The Jurassic Mammalia have been formerly supposed to bear an 
Australian facies; but a comparison of the existing Marsupials of 
Australia with the Jurassic Allotheria and Pantotheria shows, 
however, only very limited points of connection between them. 
The Mesozoic forms exhibit a much more uniform character than 
their more strongly differentiated Australian relations, and the main 
agreement of the two faunas consists in the absence of placental 
genera. 
No traces of Mammalia were known from the Cretaceous form- 
ation until the year 1882. Now, isolated teeth of the genus 
Plagiaulax, already known in the Jurassic, have been found in the 
English Wealden, and from the so-called Laramie-beds of Western 
America a notable number of teeth and fragments of jaws have been 
described by Marsh. ‘The hopes which had been earlier entertained 
of the discovery of Cretaceous Mammalia, have not been altogether 
fulfilled, for those which have been found up to the present indicate 
that the Jurassic forms had passed through but slight changes in the 
Cretaceous Epoch, and that Allotheria, Pantotheria, and perhaps a 
Tillodont-genus (Stagodon) still constituted the primitive stock of 
the Mammalian fauna of this period. The expected precursors of 
the Ungulates, Carnivora, Rodents, and other placental orders have 
not been discovered. The numerous genera founded by Marsh on 
detached teeth have been greatly reduced by Osborn; the, in some 
measure, well-grounded forms, such as Meniscoéssus, Cimolomys, 
Allacodon and Oracodon are closely connected with the Jurassic 
Allotheria, or, such as Dryolestes and Pediomys, with the Pantotheria. 
Some small jaws and teeth referred to Didelphops, Cimolestes, 
Telacodon and Batodon appear to be genuine Marsupials (Didel- 
phyide). Thus the diminutive forms of the Cretaceous Mammalian 
fauna appear to be an extension of the Jurassic and not the 
forerunners from which the infinitely richer and more varied 
Tertiary fauna can be traced. 
With the beginning of the Tertiary era the sources of our know- 
ledge of fossil Mammalia are much more abundant than in the 
Mesozoic period. 
