ZOOLOGY. 111 
coloration from each other the females will be so similar in their 
plain markings as to make it almost impossible to separate 
them. There is also considerable variation in the shape of the 
fins between the males and females of some species, especially 
noticeable in the genus Catonotus, in which the spiny dorsal fin 
of the male is short and each ray usually terminates in a little 
knob, while in the female the rays are longer, and are without the 
Fig. 5. 
ll Wt MY 
SAP PS Renee Rees wane decbsan = 
WS ‘ 
Hyostoma, 
eee 
knob. Pages could be written on the variations which individ- 
uals of the different species exhibit when a large number of any 
one species has been carefully examined, but enough has been 
said here to call attention to the necessity of securing all the ma- 
terial possible for the work on which I am engaged. 
These small fishes have the general appearance of young perch, 
and combine the habits of the perches with those of the little fresh 
water bull heads (Cottoids) or “ miller’s thumbs” as they are 
called in England. 
They are found in 
nearly all locations, 
including lakes, 
ponds, rivers, small 
streams and ditches. 
The sandy and gray- 
elly shores of lakes APT 
and ponds are favorite spots, as well as the grass and weed grown 
shallow parts of rivers, or the clear rocky stream. Several of the 
species are in great part surface swimmers, but by far the larger 
number pass most of their time on the bottom, darting about from 
stone to stone or in and out among the water plants. From this 
habit of moving by quick, short, and often zig-zag darts they Asi 
received the common and very appropriate name of ‘darte 
and in many localities are well known under that name. A few 
