PERCID^. — LXIII. 121 



Family LXIII. PERCID^. (The Perches.) 



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- 

 dobranchiae 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 caeca few ; vertebrae more 

 numerous than in Serranidce, 30 to 45. Genera about 7 ; species 

 about 1 00, in the fresh waters of the Eastern United States, Europe 

 and Northern Asia. The gi-eat majority of the species belong to 

 the singular genus or subfamily, Etheosioma, including the Darters, 

 a most singular group of dwarfed perches, peculiar to the waters of 

 Eastern America. 



a. Pseudobranchise imperfect or wanting ; preopercle entire or nearly so; 

 branchiostegals 6; anal papilla usually present; pyloric casca 2 or 3; 

 supraoccipital crest low; tishes of small size {Etheostomatina). 



Etheostoma, 158. 

 aa. Pseudobranchiae well developed ; preopercle serrate, the teeth on its lower 

 margin retrorse; branchiostegals?; no anal papilla; premaxillaries 

 protractile; size large. (PercincB.) 



b. Canine teeth none; body oblong Perca, 159. 



bb. Canine teeth on jaws and palatines; body elongate. 



Stizostedion, 160. 



158. ETHEOSTOMA Rafinesque. Darters. 



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 osteology ^ of the species, except in regard to the numbers of 

 the vertebrae. 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- 



1 For an account of the osteoloKy of this group, see Jordan & Eigenmann, Proc. 

 V. S. Nat. Mus. 1885, 68. For a popular account of the habits of the species, see 

 Jordan & Copelaud on " Johnny Darters," in " Science Sketches." 



