76 The Food of the Smaller Fresh - Water Fishes. 
to seven or eight times the length of the head and body together. 
For convenience’ sake I have grouped the genera as follows: 
Group I. — Intestine long. Pharyngeal teeth not or slightly 
hooked, with grinding surface. 
Campostoma , Pimephales , Hyborhynchus , Hybognat/ius. 
Group II. — Intestine rather long. Teeth hooked, with grinding 
surface. 
Notemigonus , Chrosomus. 
Group III. — Intestine short. Teeth hooked, with grinding sur- 
face. 
Hybopsis, Luxilus , Lythrurus , llemitremia, Platygobio. 
Group IV. — Intestine short. Teeth hooked, without grinding 
surface. 
Minnilus , Photogenis , Ericymba , Phenacobius , Semotilus , 
C eratichthys, Phinichthys. 
The second group, consisting of Notemigonus and Chrosomus, 
may be again divided according to the development of the gill- 
rakers, which are numerous, long, and slender in Notemigonus; 
few, short, and insignificant in Chrosomus. 
Food of the Young. 
The genera and species of Cyprinidae are not easily recognized, 
even in the adult, the characters upon which they are based being 
often either trivial or extremely variable; and when one has to 
do with individuals small enough to show the earliest food of the 
family, it is commonly quite impossible to identify even the genus. 
In the few specimens which I have studied, I have not attempted 
such determination, although I have reason to believe that most 
of those examined belong to some species of Minnilus. 
Their food was so far peculiar, as compared with the young of 
other families, that 1 will describe in detail that found by dissect- 
ing six specimens under an inch in length. The first of these, 
three-eighths of an inch long, taken in Fox River on the 8th of 
July, had eaten only a small Chironomus larva, and a single ex- 
ample of Bosmina. Two specimens, six-tenths of an inch long, 
captured in August in a creek in Central Illinois, had derived 
their food from quite different sources. Filaments of Spirogyra 
and other filamentous Algte, cells of Cosmarium and Closterium, 
