230 FISHES OF ILLINOIS 



green, and silvery sometimes visible; the entire bodies of breeding males 

 often almost black. Head broad below, depressed, the profile concave, 

 2.8 to 3.2; width of head 1 . S 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 jaws 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 abun- 

 dantly 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 situations it most affects are those in 

 which there is little or no current and a muddy bottom, our coeffi- 

 cient 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, 



*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. Xat. 

 Mus., Pt. I., p. 7.S7). 



