208 SMITHSONIAN MISCELLANEOUS COLLECTIONS [voL. 48 
species, and (2) the comparative relations of the species to the old 
world faunas. 
The isolation of America’s cyprinoid fauna affords one of the 
many arguments against the association of all the northern faunas 
into one great realm or region variously designated as the triarctic, 
holarctic, and periarctic. 
The American Cyprinids may be segregated under two geograph- 
ical divisions, one including the species of the Atlantic slope as well 
as of the Mississippi Valley, and the other those of the Pacific slope. 
The former are the most characteristically American, the latter most 
nearly related to old world forms. It has long been maintained by 
botanists—by many at least—that there is a striking analogy on the 
one hand between the types of eastern America and eastern Asia, 
and on the other between those of western America and western 
Europe. Some features of the fish faunas might seem to support 
such a contention, but a more critical consideration of the evidence 
leads to a different conclusion. The fauna of Europe extends east- 
ward into Asia and the resemblance between the fish faunas of 
western America and Europe is simply due to that fact and to the 
approximation of the two continents toward the north. 
Another noteworthy circumstance is the large size which many 
of the Cyprinids of the Pacific slope attain, in this respect rivaling 
old world species, and con- 
trasting with those of the 
cismontane regions. On the 
other hand, almost all of the 
numerous Cyprinids, not only 
of the streams of the Atlantic 
slope, but of the great Mis- 
sippi Valley, are of small size, 
only a couple of species under 
ordinary circumstances reach- 
ing a length of a foot. The 
large Cyprinids of Europe are to some extent replaced by the 
Catosomids (suckers) of America. 
In more detail, none of the American species have three rows 
of pharyngeal teeth as most of the old world forms have. Fur- |; 
ther, a rather striking feature is the reduction in the number of 
pharyngeal teeth in the main row; the European species generally 
have five (in very few less) while most of the American species have 
only four. The Chondrostomines of Europe have mostly six or 
Fic. 36.—Pharyngeal bones and teeth of 
Chondrostoma nasus. After Heckel. 
