The Ganoids 261 
ally common throughout the Mississippi Valley. It has a short 
broad snout like the alligator gar, but seldom exceeds three feet 
in length. In size, color, and habits it agrees closely with the 
common gar, differing only in the form of the snout. The form 
is subject to much variation, and it is possible that two or more 
species have been confounded. 
The great alligator-gar, Lepisosteus tristechus, reaches a 
length of twenty feet or more, and is a notable inhabitant of 
the streams about the Gulf of Mexico. Its snout is broad and 
relatively wide, and its teeth are very strong. It is very de- 
structive to all sorts of food-fishes. Its flesh is worthless, and 
its enameled scales resist a spear or sometimes even shot. 
Fia. 197.—Alligator-gar, Lepisosteus tristechus (Bloch). Cuba. 
It breathes air to a certain extent by its lungs, but soon dies 
in foul water, not having the tenacity of life seen in Amza. 
Order Halecomorphi.—To this order belong the allies, living 
or extinct, of the bowfin (Amza), having for the most part 
cycloid scales and vertebrae approaching those of ordinary 
fishes. The resemblance to the Jsospondyli, or herring group, 
is indicated in the name (Halec, a herring; sopd7), form). The 
notochord is persistent, the vertebrz variously ossified. The 
opercles are always complete. The branchiostegals are broad 
and there is always a gular plate. The teeth are pointed, usually 
strong. There is no infraclavicle. Fulcra are present or 
absent. The supports of the dorsal and anal are equal in num- 
ber to the rays. Tail heterocercal. Scales thin, mostly cycloid, 
but bony at base, not jointed with each other. Mandible com- 
plex, with well-developed splenial rising into a coronoid process, 
which is completed by a distinct coronoid bone. Pectoral fin 
with more than five actinosts; scales ganoid or cycloid. In the 
living forms the air-bladder is connected with the cesophagus 
through life; optic chiasma present; intestine with a spiral 
valve. 
