306 Percoidea, or Perch-like Fishes 



gate in body, with the vertebrae in increased number and with 

 only two spines in the anal fin. About ninety species are 

 recorded, the vast majority being American. The dwarf perches, 

 called darters (Etheostomince) , are especially characteristic of 

 the clear streams to the eastward of the plains of the Missouri. 

 These constitute one of the greatest attractions of our American 

 river fauna. They differ from the perch and its European allies in 

 their small size, bright colors, and large fins, and more technic- 

 ally in the rudimentary condition of the pseudobranchiae and 

 the air-bladder, both of which organs are almost inappreciable. 

 The preopercle is unarmed, and the number of the branchioste- 

 gals is six. The anal papilla is likewise developed, as in the 

 GobiidcB, to which group the darters bear a considerable super- 

 ficial resemblance, which, however, indicates no real affinity. 

 Relations of Darters to Perches. The colors of the Ethe- 

 ostomincz, or darters, are usually very brilliant, species of 

 Etheostoma especially being among the most brilliantly colored 

 fishes known; the sexual differences are often great, the females 

 being, as a rule, dull in color and more speckled or barred than 

 the males. Most of them prefer clear running water, where 

 they lie on the bottom concealed under stones, darting, when 

 frightened or hungry, with great velocity for a short distance, 

 by a powerful movement of the fan-shaped pectorals, then 

 stopping as suddenly. They rarely use the caudal fin in swim- 

 ming, and they are seldom seen floating or moving freely in 

 the water like most fishes. When at rest they support them- 

 selves on their expanded ventrals and anal fin. All of them 

 can turn the head from side to side, and they frequently lie 

 with the head in a curved position or partly on one side of the 

 body. The species of Ammocrypta, and perhaps some of the 

 others, prefer a sandy bottom, where, by a sudden plunge, 

 the fish buries itself in the sand, and remains quiescent for 

 hours at a time with only its eyes and snout visible. The 

 others lurk in stony places, under rocks and weeds. Although 

 more than usually tenacious of vitality, the darters, from their 

 bottom life, are the first to be disturbed by impurities in the 

 water. All the darters are carnivorous, feeding chiefly on the 

 larvae of Diptera, and in their way voracious. All are of small 

 size; the largest (Percina rex} reaches a length of ten inches, 



