Percoidea, or Perch-like Fishes 509 
variously developed, but always with some spines in front, 
these typically stiff and pungent; anal fin typically short, 
usually with three spines, sometimes with a larger number, 
rarely with none; caudal fin various, usually lunate; pectoral 
fins well developed, inserted high; ventral fins always present, 
thoracic, separate, almost always with one spine and five rays, 
the Aphredoderide having more, a few Serranide having fewer. 
Air-bladder usually present, without air-duct in adult; simple 
and generally adherent to the walls of the abdomen. Stomach 
cecal, with pyloric appendages, the intestines short in most 
species, long in the herbivorous forms. Vertebral column well 
developed, none of the vertebree especially modified, the number 
1o+14=24, except in certain extratropical and fresh-water 
forms, which retain primitive higher numbers. Shoulder-girdle 
normally developed, the post-temporal bifurcate attached to the 
skull, but not coossified with it; none of the epipleural bones 
attached to the center of the vertebrae; coracoids normal, the 
hypercoracoid always with a median foramen, the basal bones of 
the pectoral (actinosts or pterygials) normally developed, three or 
four in number, hour-glass-shaped, longer than broad; premaxil- 
lary forming the border of the mouth usually protractile; bones 
of the mandible distinct. Orbitosphenoid wanting. 
The most archaic of the perch-like types are apparently 
some of those of the fresh waters. Among these the process 
of evolution has been less rapid. In some groups, as the 
Percide, the great variability of species is doubtless due to 
the recent origin, the characters not being well fixed. 
The Pirate-perches: Aphredoderide.— Among the most re- 
markable of the living percoid fishes and probably the most 
primitive of all, showing affinities with the Salmoperce, is the 
Pirate-perch, Aphredoderus sayanus, a little fish of the low- 
land streams of the Mississippi Valley. The family of Aphre- 
doderide agrees with the berycoid fishes in scales and structure 
of the fins, and Boulenger places it with the Berycide. Starks 
has shown, however, that it lacks the orbitosphenoid, and the 
general osteology is that of the perch-like fishes. The dorsal 
and anal have a few spines. The thoracic ventrals have one 
spine and eight rays. There is no adipose fin and probably no 
duct to the air-bladder. A singular trait is found in the posi- 
