AA. 
KEY TO FAMILIES. 17 
Class: PISCES. 
Sub-Class: 'TELEOSTOMI (True Fishes). 
Artificial Key to the Families of Fishes. 
I. VENTRAL FINS PRESENT—ABDOMINAL. 
Back with an adipose fin behind the single, rayed dorsal fin. 
B. Head with barbels about mouth and nostrils, body scaleless; a single spine in 
each pectoral and in dorsal fin.— SILURID2. 
BB. Head without barbels ; body scaled. 
C. Dorsal, anal and ventral fins each with a small but distinct spine; scales 
ctenoid.— PERCOPSID &, 
CC. Dorsal, anal, and ventrals without distinct spine; scales not ctenoid.— 
SALMONID 2. 
Back without adipose fin. 
D. Dorsal fin single, composed of rays, and not preceded by a series of free spines. 
E. Tail evidently strongly heterocercal. 
F. Body naked; snout with a spatulate blade; mouth wide, without 
barbels.— POLYODONTID.®. 
FF. Body with scales or bony plates or shields. 
G. Body with 5 series of bony shields; mouth inferior, tooth- 
less, preceded by four barbels.— ACIPENSERID2. 
GG. Body scaly. 
H. Scales cycloid; a broad, bony, gular plate; dorsal fin 
many rayed.— AMIID. 
HH. Scales ganoid ; no gular plate ; dorsal fin short.— 
LEPISOSTEID®. 
EE. Tail not evidently heterocercal. 
- Gill membranes broadly joined to the isthmus; head naked; no 
teeth in jaws. 
A Lower pharyngeal teeth very numerous, in one row like the 
teeth of a comb.— CATOSTOMID. 
JJ. Lower pharyngeal teeth few, fewer than 8, in 1 to3 rows.— 
CYPRINID2. 
II. Gill membranes free, not attached to the isthmus. 
K. Head scaly, more or less. 
1 Upper jaw not protractile, its lateral margins formed by 
the maxillaries. 
M. Jaws depressed, prolonged ; lateral line present.— 
LuciDz. 
MM. Jaws short ; no lateral line.— UMBERID 2. 
LL. Upper jaw protractile, its margin formed by premaxil- 
laries alone; no lateral line.— POECILIID. 
KK. Head naked. 
N. Lateral line well developed; mouth large, teeth all 
pointed, some of them canine.— HIODONTID®. 
NN. Lateral line wanting. 
oO. Mouth small, inferior, toothless ; stomach gizzard- 
like.— DOROSOMATID®. 
OO. Mouth moderate, terminal; stomach not gizzard- 
like.— CLUPEID®. 
