144 J^J^<^ American Geologist. September, 1*99 
taken by him. The amphil)ians also claimed but little atten- 
tion, and his observations on the metamorphosis of the recent 
Siredon into Amblysoma, and two brief notices of amphibian 
footprints in the Devonian and Carboniferous comprise the 
whole. 
It is with extreme hesitation and a sense of inadequacy that 
the writer ventures to review, even in the briefest and most 
superficial manner, the work which undoubtedly constitutes 
the literary essence of his life-work. Future investigators 
alone can critically estimate the great mass of facts vvhich 
Marsh brought out and which he wove into the departments 
of fossil reptiles, birds, and mammals. 
His most comprehensive work, and in many ways the most 
masterly, is the address delivered before the American Asso- 
ciation for the Advancement of Science, at Nashville, in 1877. 
In this paper, entitled the "Introduction and Succession of 
Vertebrate Life in America," he traced the introduction of the 
various types of vertebrate life then known in America, begin- 
ning with the lowest fishes and ending with man. The amount 
of knowledge on the lower classes of vertebrates, including the 
reptiles, was then too meager to enable him to give more than 
occasional hints as to their phylogeny. But his handling of 
the Mammalia showed the clearest insight into the develop- 
ment and affinities of many of the important types, and marked 
him as a true philosopher. 
A glance at the modern text-books of geology and paleon- 
tology reveals how much America has done for the fossil ver- 
tebrates in the three classes of reptiles, birds, and mammals. 
It will also show that Marsh contributed more than any other 
investigator toward the prominence now accorded to the 
American forms. 
His work on the Reptilia is not equally divided among the 
various orders, for the Dinosauria claimed his attention above 
all others. To this group he lent his best efforts, and he com- 
passed it so thoroughly as to be its sole master. It seems only 
necessary in this place to notice the complete restorations he 
made of some of these remarkable animals. In this list are 
included Anchisaurus, Brontosaurus , Laosmirus, Cerato- 
smtrns, Camptosaurns, Stegosaurns, Triceratops, and Clao- 
saurns. It must be remembered that nearly all these animals 
