1876.] A Century's Progress in American Zodlogy. 595 
nighest rank among systematic works. Numerous fossil forms 
have been brought to light by Hall, Billings, Meek, Shumard, 
White, Whitfield, W. H. Niles, O. A. Derby, and other palæon- 
tologists, and the distribution of the recent forms on bot: sides 
of the continent has been studied by Verrill and A. Agassiz. 
The Sponges have been chiefly studied by Clark and Hyatt ; 
and the Protozoa by J. W. Bailey, Clark, Leidy, and Tuttle. 
We may congratulate ourselves on the high position of our 
palzontologists in the scientific world. The labors of James 
Hall, Meek, Billings, Dawson (of Montreal; we have included 
Canadian students in this article), and others have revealed 
whole platforms of life in the Paleozoic rocks; while the re- 
searches of Leidy, Marsh, and Cope in the Tertiary and Creta- 
ceous beds of New Jersey and the West, and of Deane, Hitch- 
cock, Leidy, Wyman, Newberry, Emmons, and Cope in Triassic 
and Carboniferous strata, have been productive of valuable re- 
sults. 
The discovery of the fossil bird-like reptiles of New Jersey, 
by Leidy and Cope; of birds with teeth and pterodactyls with- 
out teeth ; of lemur-like monkeys, by Marsh; and the discovery 
by Leidy, Marsh, and Cope of connecting links between living 
ruminants and hog-like forms, and between elephants and tapirs ; 
together with the genealogy of the horse, and the increase in the 
size of the brain of living forms over their Tertiary ancestors, as 
elaborated by Marsh, all present a mass of new facts bearing on 
the evolution of life on the American continent and the general 
doctrine of evolution. 
In philosophical zodlogy Dana’s papers on Cephalization, and 
yman’s views on the Vertebrate Theory of the Skull, in his 
Memoir on Rana pipiens, and his studies on antero-posterior 
symmetry in vertebrates ; those of James Hall on the succession 
of molluscan life in palzozoie rocks; and those of Agassiz on 
Ptophetic and synthetic types, and laws of embryological growth 
àS correlated with the succession of extinct forms, with other views 
n his Essay on Classification, should be here cited. The deep- 
Sea researches of L. F. de Pourtales on the coast of Florida enabled 
him to state that “ animal life exists at great depths in as great a 
diversity and as great an abundance as in shallow water.” This 
Was in 1867, before the cruise of the English steamer Porcu- 
Pine and the researches of Carpenter, Thompson, and Jeffreys. 
The epoch of embryology or the developmental study of 
ammals was inaugurated by Agassiz in 1846. In the publica- 
