The Ganoids 251 
with very long dorsal and anal fins. In other respects they are 
very similar to the Palgoniscide, the osteology being the same. 
The Palgoniscide were rapacious fishes with sharp teeth, the 
Platysomide less active, and, from the blunter teeth, probably 
feeding on small animals, as crabs and snails. 
The rhombic enameled scales are highly specialized and 
held together as a coat of mail by peg-and-socket joints. The 
most extreme form is Platysomus, with the body very deep. 
Platysomus gibbosus and other species occur in the Permian 
rocks of Germany. Cheirodus is similar to Platysomus, but 
without ventral fins. Eurynotus, the most primitive genus, is 
remarkable for its large pectoral fins. Eurynotus crenatus occurs 
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Fie. 186.—Eurynotus crenatus Agassiz, restored. Carboniferous. Family 
Platysomide. (After Traquair.) 
in the Subcarboniferous of Scotland. Other genera are Meso- 
lepis, Globulodus, Wardichthys, and Chetrodopsts. 
Some of the Platysomide have the interneural spines pro- 
jecting through the skin before the dorsal fin. This condition 
is found also in certain bony fishes allied to the Carangide. 
The Dorypteride.—Dorypterus hoffmant, the type of the sin- 
gular Paleozoic family of Dorypteride, with thoracic or sub- 
jugular many-rayed ventrals, is Stromateus-like to all appear- 
ance, with distinct resemblances to certain Scombroid forms, 
but with a heterocercal tail like a ganoid, imperfectly ossified 
back-bone, and other very archaic characters. The body is 
apparently scaleless, unlike the true Platysomide, in which the 
