230 FISHES OF ILLINOIS 



light coppery, green, and silvery sometimes visible; the entire bodies of 

 breeding males often almost black. Head broad below, depressed, the pro- 

 file concave, 2.8 to 3.2; width of head 1.5 to 1.8 in its length; interorbital 

 space 3.3 to 4; eye 1.4 to 1.8 in interorbital, 4.5 to 5.3 in head; nose 2.8 to 

 3.4 (usually less than 3.2); mouth moderate, oblique, maxillary nearly to 

 front of orbit, 2.7 to 2.9; lower jaw projecting; sides and top of head, chin, 

 and lower jaw with rows of sensory papillae, as in Amblyopsidce. Dorsal III, 

 9-12 (usually 10 or 11), the fin nearer muzzle than base of caudal, behind 

 ventrals; caudal fin broadly rounded, with a slight notch; anal II, 6; ventrals 

 jugular in adult*, nearer angle of gill-membranes than front of anal; pectorals 

 1.4 to 1.8 in head, reaching more than half way to anal. Scales 9-13 (usually 

 11-12), 49-59, 12-14, strongly ctenoid; lateral line developed anteriorly; 

 cheeks and opercles fully scaled. 



This obscure but peculiar little fish has been found by us in 

 muddy pools and streams throughout Illinois, much the most 

 abundantly southward. It is indeed so rare in northern Illinois 

 that only one of our hundred collections of it has been taken in 

 that part of the state, giving us a frequency coefficient of less 

 than 5 per cent., while that for central Illinois is .72 and that for 

 southern Illinois is 2.23. We have found it most abundant in 

 creeks (coefficient, 2.51), and about half as common in large 

 rivers (1.1) and in lowland lakes (1.24). The streams and situa- 

 tions it most affects are those in which there is little or no current 

 and a muddy bottom, our coefficient of the species for quiet 

 water being 3.26, and that for a muddy bottom, 3.26. 



The general distribution of the pirate-perch carries it from 

 Long Island around the coasts of the Atlantic and the Gulf to 

 Texas, and northward up the Mississippi basin to South Dakota 

 and Minnesota and through the Great Lakes at least as far east 

 as Lake Erie. It has not been reported from Canada. 



It was named the " pirate-perch " by Dr. C. C. Abbott, 

 because it ate only fishes when confined in his aquarium. Studies 

 made by us in Illinois show, however, that fishes form only a 

 small part of its normal food. The intestine is short and simple, 

 less than the length of the head and body without the tail; the 

 gill-rakers are short, thick, blunt, and few, and covered with 

 short spinules; and the pharyngeal jaws are small plates covered 

 with short, sharp, minute teeth, similar to those of the sunfishes. 

 The mouth is large, but not remarkably protractile. Judging 

 from 19 specimens dissected, the food is virtually all animal. 

 Small fishes had been eaten by but two, the only one recogniza- 

 ble being a minnow (Cyprinidce) . Insects formed the major 



* On variability in position of vent with age, see Jordan (Bull. 111. State Lab. Nat. Hist., 

 No. 2. 1878, p. 48), and Jordan and Evermann (Bull. 47, U. S. Nat. Mus., Pt. I., p. 787). 



