102 SCIENCE SKETCHES. 
species still found in the sea along our coasts. 
Other species are anadromous, ascending the rivers 
in the spring. 
The Gizzard-shad is indifferently marine, anad- 
romous, or landlocked, and is still extending its 
range in sluggish waters through the agency of 
canals. 
The various forms of Sa/monide abound in the 
streams and lakes of all northern regions. The larger 
species are marine and anadromous, the smaller 
confined to lakes and brooks; but all seek streams 
or at least shallower waters for the purpose of 
spawning. The whole group had probably a ma- 
rine origin; the more strictly fresh-water species 
being, as is usually the case, smaller in size, weaker 
in organization, and with feebler dentition. It is 
often assumed that this group has had its origin 
in the Atlantic; but whether in America or in 
Europe, we have no means of inferring. 
The Zvout-perch show a curious combination of 
characters of spiny and soft-rayed fishes. The sin- 
gle species is probably, as suggested by Agassiz, a 
relic of an ancient fauna. 
The Blindfishes are also very unique in their 
organization. Two of the known species have 
well-developed eyes, and live in lowland streams 
and springs. Such are doubtless ancestors of the 
eyeless forms of the cave streams, but the imme- 
diate progenitors and relatives of these seem to be 
extinct. They were probably fresh-water rather 
than marine forms, and of the same general stock 
as the ancestors of the Killifishes, Mud-minnows, 
and Pike. 
