O. C. Marsh— Vertebrate Infe in America, 339 
According to present knowledge, no vertebrate life is known 
to have existed on this continent in the Archean, Cambrian, or 
exist here in those remote ages. Fishes are known Sr the 
Upper Silurian of Europe, and there is every probability that 
they will yet be discovere in our strata of the same age, if not 
at a still lower horiz 
In the shore pease of the early Devonian sea, known as 
the Schoharie Grit, characteristic peneaee of Fishes were pre- 
served, and in the deeper sea that followed, in which the 
continue abundant in the shallower seas, and, so far as now 
known, were the only type of vertebrate life. 7 fishes 
were mainly Seceae a group, represented in our present 
waters by the Gar- -pike (Lepidosteus) and Sturgeon (Aipensr 
but, in the Devonian sea, chiefly by the aes ee, the ex 
affinities of which are somewhat in doubt, ith these were 
Elasmobranchs, or the ne, tribe, and among them a few 
epimers a peculiar r type, of which one or two members still 
survive. ‘The Placoderms were the monarchs of the ocean. All 
were gu protected by a massive coat -of armor, and some o 
them attained huge dimensions. The American Devonian fishes 
now known are not as numerous as those of Europe, but they 
were larger in size, and mostly inhabitants of the open sea. 
Some twenty genera and forty species have been described. 
e more important genera of Placoderms are, Dinichthys, 
Aspidichthys, and Dee our largest Paleozoic fishes. 
Others are, Acanthaspis, Acantholepis, Coccosteus, Macropetalich- 
oys, and Onychodus. Among the Elasmobranchs were, Clado-: 
dus, Nechaiath us, Machcracanthus, Rhynchodus, and Ptyctodus, 
the last two ang regarded as ohamttia ve the Chemung 
epoch, the great sha gy a was introduced with Dipierus, 
Heliodus, and possi Ceratodus. Species of the European 
legmtis Bothriolepis an Sega oes have likewise been found 
ur Devonian de 
With the close of tha Davekian. came the almost total extine- 
Helodus, Psammodus and Sandalodus. Of the Sarangi 
there were Antliodus, Chomatodus, Ctenoptychius, Petalodus an 
