The Ganoids 34 
to have the ‘‘mandibular ramus without or with a reduced 
fissure of the dental foramen, and without the groove con- 
tinuous with it in Lepisosteus. One series of large teeth, with 
_ small ones external to them on the dentary bone.’’ Most of 
the fossil forms belong to Clastes, but the genus shows no differ- 
ence of importance which will distinguish it from the ordinary 
garpike. 
Order Halecomorphi.—To this order belong the allies, living 
or extinct, of the bowfin (Amia), having for the most part 
cycloid scales and vertebre approaching those of ordinary 
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fishes. The resemblance to the Jsospondyli, or herring group, 
is indicated in the name (Halec, a herring; popdy, 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. This group corresponds to the Amioider of Liitken 
ll—3 
