PRESIDENTIAL ADDRESS. 467 
features; and birds have been toothless since the end of Cretaceous times. 
The monotreme mammals of Australasia, which are really a survival from 
the Jurassic period, are also toothless. Some of the latest Ichthyosaurs and 
Pterodactyls were almost or quite toothless ; and I have seen a jaw of an 
Upper Cretaceous carnivorous Dinosaur (Genyodectes) from Patagonia so 
completely destitute of successional teeth that it seems likely some of these 
land reptiles nearly arrived at the same condition. 
Among fishes there is often observable still another sign of racial old 
age—namely, their degeneration into eel-shaped forms. The Dipnoan fishes 
afford a striking illustration, beginning with the normally shaped Dipterus 
in the Middle Devonian, and ending in the long-bodied Lepidosiren and 
Protopterus of the present day. The Paleozoic Acanthodian sharks, as 
they are traced upwards from their beginning in the Lower Devonian to 
their end in the Permian, also acquire a remarkable elongation of the body 
and a fringe-like extension of the fins. Among higher fishes, too, there are 
numerous instances of the same phenomenon, but in most of these the 
ancestors still remain undiscovered, and it would therefore be tedious to 
discuss them. 
Finally, in connection with these obvious symptoms of old age in races, 
it is interesting to refer to a few strange cases of the rapid disappearance 
of whole orders of animals, which had a practically world-wide distribution 
at the time when the end came. Local extinction, or the disappearance of 
a group of restricted geographical range, may be explained by accidents of 
many kinds; but contemporaneous universal extinction of widely spread 
groups, which are apparently not affected by any new competitors, is not 
so easily understood. The Dinosaurs, for instance, are known to have lived 
in nearly all lands until the close of the Cretaceous period; and, except 
perhaps in Patagonia, they were always accompanied until the end by a 
typically Mesozoic fauna. Their remains are abundant in the Wealden 
formation of Western Europe, the deposit of a river which must have 
_drained a great continent at the beginning of the Cretaceous period ; they 
have also been found in a corresponding formation which covers a large 
area in the State of Bahia, in Brazil. They occur in great numbers in the 
freshwater Upper Cretaceous Laramie deposits of Western North America, 
and also in a similar formation of equally late date in Transylvania, 
South-East Europe. In only two of these regions (South-Hast England 
and West North America) have any traces of mammals been found, and they 
are extremely rare fragments of animals as small as rats; so there is no 
reason to suppose that the Dinosaurs suffered in the least from any struggle 
with warm-blooded competitors. Even in Patagonia, where the associated 
mammal-remains belong to slightly larger and more modern animals, these 
fossils are also rare, and there is nothing to suggest competition. The race 
of Dinosaurs seems, therefore, to have died a natural death. The same may 
be said of the marine reptiles of the orders Ichthyosauria, Plesiosauria, and 
Mosasauria. They had a practically world-wide distribution in the seas of 
the Cretaceous period, and the Mosasauria especially must have been 
extremely abundant and flourishing. Nevertheless, at the end of Cretaceous 
times they disappeared everywhere, and there was absolutely nothing to 
take their place until the latter part of the Eocene period, when whales and 
porpoises began to play exactly the same part. So far as we know, the 
higher race never even came in contact with the lower race; the marine 
mammals found the seas vacant, except for a few turtles and for one curious 
Rhynchocephalian reptile (Champsosaurus), which did not long survive. 
Another illustration of the same phenomenon is probably afforded by the 
primitive Carnivora (the so-called Sparassodonta), which were numerous in 
South America in the Lower Tertiary periods. They were animals with a 
brain as small as that of the thylacines and dasyures which now live in 
Tasmania. They appear to have died out completely before they were 
HH 2 
