PERCIDA, — LXIIL 121 
Famity LXUI. PERCIDAX. (THE PEeRcues.) 
Body elongate, with rather small ctenoid, adherent scales; lateral 
line usually present, not extending on caudal fin; mouth various, 
the teeth usually villiform ; no supplemental maxillary ; opercle with 
a flat spine; B. 6 or 7; gills 4, a slit behind the fourth; gill mem- 
branes free from isthmus; gill rakers slender, toothed; pseu- 
dobranchie small, often concealed by skin; lower pharyngeals 
separate, with sharp teeth; air-bladder usually small or wanting, 
adherent to abdominal walls. Fins usually large; dorsal fins sepa- 
rate, the first with 6 to 15 spines; anal spines 1 or 2; V. thoracic, 
I, 5; intestinal canal short; pyloric ceca few; vertebrae more 
numerous than in Serranide, 30 to 45. Genera about 7; species 
about 100, in the fresh waters of the Eastern United States, Europe 
and Northern Asia. The great majority of the species belong to 
the singular genus or subfamily, Etheostoma, including the Darters, 
a most singular group of dwarfed perches, peculiar to the waters of 
Eastern America. 
a. Pseudobranchie imperfect or wanting ; preopercle entire or nearly so; 
branchiostegals 6; anal papilla usually present; pyloric ceca 2 or 3; 
supraoccipital crest low; tishes of small size (EZtheostomatine). 
ETHEOSTOMA, 158. 
aa. Pseudobranchie well developed; preopercle serrate, the teeth on its lower 
margin retrorse; branchiostegals 7; no anal papilla; premaxillaries 
protractile; size large. (Percine.) 
&. Canine teeth none; body oblong... . . Cane - » Perca, 159, 
66. Canine teeth on jaws and palatines; body elongate. 
STIZosTEDION, 160. 
158. ETHEOSTOMA Rafinesque. Darrers. 
This group comprises a great variety of forms, and it has been 
usually divided into 10 to 16 genera. It is, however, impossible to 
maintain most of these subordinate groups as genera on account of 
intergradations of all sorts. There is no considerable variation in 
the osteology1 of the species, except in regard to the numbers of 
the vertebre. The group is apparently one of comparatively recent 
origin, and the differential characters do not seem to have become 
very firmly fixed. On the other hand, the extremes of the group 
(as E. pellucidum or E. microperca) have diverged very far from 
their perch-like ancestors. 
The relations of the Darters to the Perches have been aptly ex- 
pressed by Dr. Stephen A. Forbes: “Given a supply of certain 
kinds of food nearly inaccessible to the ordinary fish, it is to be ex- 
pected that some fishes will become especially fitted for its utiliza- 
2 For an account of the osteology of this group, see Jordan & Eigenmann, Proc. 
U. 8S. Nat. Mus. 1885, 68. For a popular account of the habits of the species, see 
Jordan & Copeland on “ Johnvy Darters,” in “Science Sketches.” 
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