294 Percoidea, or Perch-like Fishes 



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 Aphredoderida? having more, a few Serranidcs having fewer. 

 Air-bladder usually present, without air-duct in adult; simple 

 and generally adherent to the walls of the abdomen. Stomach 

 cascal, with pyloric appendages, the intestines short in most 

 species, long in the herbivorous forms. Vertebral column well 

 developed, none of the vertebrae especially modified, the number 

 10 + 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 

 Percidce, the great variability of species is doubtless due to 

 the recent origin, the characters not being well fixed. 



The Pirate-perches : Aphredoderidae. Among the most re- 

 markable of the living percoid fishes and probably the most 

 primitive of all, showing affinities with the Salmopercce, is the 

 pirate-perch, Aphredoderus say anus, a little fish of the low- 

 land streams of the Mississippi Valley. The family of Aphre- 

 doderid agrees with the berycoid fishes in scales and structure 

 of the fins, and Boulenger places it with the Berycidae. 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- 



