Dr. A. S. Woodu-ard's Presidential Address. 417 



and larger, as we see them in the familiar cases of the horses and 

 elephants of the I^orthern Hemisphere and the hoofed animals and 

 armadillos of South America. 



Another frequent mark of old age in races was first discussed 

 and clearly pointed out by the late Professor C. E. Beecher, of Yale. 

 It is the tendency in all animals with skeletons to produce 

 a superfluity of dead matter, which accumulates in the form of 

 spines or bosses as soon as the race they represent has reached its 

 prime and begins to be on the down grade. Among familiar instances 

 may be mentioned the curiously spiny Graptolites at the end of 

 the Silurian period, the horned Pariasaurians at the beginning of 

 the Trias, the armour-plated and horned Dinosaurs at the end 

 of the Cretaceous, and the cattle or deer of modern Tertiary times. 

 The last case — that of the deer — is specially interesting, because 

 fossils reveal practically all the stages in the gradual development 

 of the horns or antlers, from the hornless condition of the Oligocene 

 species, through the simply forked small antlers of the Miocene 

 species, to the largest and most complex of all antlers seen in Cerviis 

 sedgwicki from the Upper Pliocene and the Irish deer ( C. (jiganteus) 

 of still later times. 



* 1^1 i¥ 1^ :a.' * 5^' 



Finally, in connexion 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 

 worldwide 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 con- 

 temporaneous 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 typical^ Mesozoic fauna. Their remains are abundant 

 in the Wealden formation of AYestern Europe, in the deposits 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-East Europe and Western 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 worldwide distribution in the seas of the 



DECADE V. VOL. VI. — XO. IX. 27 



