510 The Geological Museum of the School of Mines, (August, 
As we pass on to the records of the next succeeding (Mesozoic) 
eras, the medizval age of geology, we find no mention made of 
the luxuriant forests and the abundant animal life that passed 
before. Nearly all remembrance of these seems lost in antiquity. 
This age, in reference to the predominating forms of life, is called 
the reptilian age. The first indications that we have of these new 
rulers of the land and sea, are their foot-prints, left along the 
muddy shores. Some of these from New Jersey and the Con- 
necticut valley are shown in the case of Triassic fossils. These 
wonderful impressions are so well known through the writings of 
Prof. Hitchcock and others, that we need do no more than men- 
tion them. The rocks in which these foot-prints were found have 
also furnished great numbers of fossil fishes. Among hundreds 
of specimens of these Triassic fishes here assembled, there is one 
called /tycholepis, with highly ornamented head-plates and plicated 
scales, which is the only American specimen known of this 
genus, which occurs in the Lias of Europe; here too is the only 
specimen yet discovered of Diplurus; this was lately obtained 
from the Triassic rocks at Boonton, N. J. The rocks of this 
age have also yielded the oldest remains known of the Mam- 
malia. This sub-kingdom makes its appearance in one of its 
humblest orders, the Marsupials, represented at the present day 
by the opossum and the kangaroo. 
In the flora of the earlier portion of this age we find ferns, 
calamites, and conifers, with the addition of a new feature, the 
Cycads. As we pass on to the cases containing the fossil plants 
from the latest period of this age, the Cretaceous, we come sud- 
denly to a splendid display of fossil leaves which have a wonder- 
fully familiar appearance; they are the leaves of oaks, willows, 
maples, beeches, sycamores, etc., which the most casual observer 
would refer to the same genera that are living at the present day. 
There are differences which show that all these fossil leaves are 
specifically distinct from their modern representatives. 
Among the most striking forms of animal life in the Mesozoic, 
were the Cephalopod shells, related to the living Nautilus. Of 
these, the ammonites which were foreshadowed by goniatites in 
the Devonian and Carboniferous, and began to assume their char- 
acteristic elegance of outline in the Triassic, in the Cretaceous 
attain a degree of variety and beauty that could with difficulty 
- be excelled. It is interesting to observe that after these mollusks 
