658 THE AMERICAN NATURALIST. [VoL. XXXII. 
place in part was filled by their probable descendants, the 
Limuli, which had already begun to appear, the earliest types 
being Neolimulus, Exapinurus, and other forms of the Silurian, 
and Protolimulus of the Devonian. The Limuli of the Carbon- 
iferous, some with short (Prestwichia and Euprodps) and others 
with long tail spines (Belinurus), suggest long possession of the 
soil and consequent variation and differentiation. 
The Eurypterida shared the fate of the trilobites, and while 
there was a thorough weeding out of the more typical ganoids, 
leaving an impoverished assemblage to live on through after 
ages, that singular primitive vertebrate group, the Ostracodermi, 
was wholly obliterated. 
On the other hand, with the incoming of a new order of 
vegetation a great outgrowth of winged insects, the represen- 
tatives of the orders of Lepidoptera and Hymenoptera, now so 
numerous in species, began their existence. 
By the close of the Appalachian revolution, probably all the 
orders of insects had originated, unless we except the most 
modified of all, the Diptera, whose remains have not been 
detected below the Lias. With but little doubt, however, the 
eight orders of holometabolous insects diverged in the Permian, 
if not near the close of the Carboniferous, from some proto- 
neuropter, the progress in the differentiation of genera and 
families becoming rapid either during the Jurassic or directly 
after the lower Cretaceous, or as soon as grasses and deciduous 
trees became in any way abundant. 
Very soon, too, after the close of the revolution, the ancestral 
birds and mammals pirena from the T and ms: the latter 
the turtles, plesi ; , crocodile ans 
and soon after the pterodactyles, came into existence. 
As a result of this revolution the molluscan type was pro- 
foundly affected, as, at the opening of the Triassic, siphoniate 
Pelecypoda, opisthobranchiate Gastropoda, and cuttles or belem- 
nites appeared. While a few orthoceratites lingered on after 
the revolution, the ammonites blossomed out in an astonishing 
variety of specific and generic forms. 
In summing up the grand results of the Appalachian revolu- 
tion and of the times immediately succeeding, we should not 
