110 ZOOLOGY. 
all the material possible before publishing the work, I take 
the Boston Society of Natural History and Peabody. Aca 
of Science, and many type specimens received from Prof. 
Hadropterus, 
and Dr. Abbott. Besides these, all the types of Girard of t 
specimens described in the Pacific Railroad and Mexican 
ary Surveys, the types of Agassiz’ species and such as still 
of Haldemann’s and Storer’s have been carefully studied. 
this material about forty species haye been recognized and se 
others are indicated by single specimens. 
_ The great variation between individuals of the same $ 
makes it essential to have a large number of specimens 170 
many localities as possible in order to determine the ape 
any degree of certainty. Especially is this variation not 
tween males, feniales and young, and between males and 
at the spawning time and those taken later in the se 
early spring the males of many of the species are most b 
arrayed in blue, orange, red, and other bright colors, whil 
‘mer and fall these colors are entirely lost or aes 
In many species where the males show a decided difer 
