168 LOWER VERTEBRATES. 



long and powerful oiled hempen or flaxen line, on a winch, with a heavy sinker ; a cod- 

 hook, baited with any kind of flesh, fish, or fowl, is the most successful, if not the most 

 orthodox or scientific, mode of capturing him. His great size and immense strength 

 alone gives him value as a fish of game ; but, when hooked, he pulls strongly and 

 fights hard, though he is a boring, deep fighter, and seldom, if ever, leaps out of the 

 water, like the true salmon and brook trout." 



In the depths of Lake Superior is a variety of the great lake trout known as the sis- 

 cowet (iSalvelinics namaycicsh, var. siscowet), remarkable for its extraordinary fatness 

 of flesh. The cause of this difference lies, jjrobably, in some peculiarity of food, as 

 yet unascertained. 



The small family of Percopsid^ may be defined, in brief, as having the form and 

 general characters of a salmonoid, with the mouth and scales of a Percoid. The pre- 

 maxillaries form the entire margin of the upper jaw, and the small teeth are found 

 only in the jaws. The bones of the head are full of mucous cavities. The fins are 

 formed essentially as in the Salraonidae. The scales are strongly ctenoid, and the 

 rather large eggs are excluded through an oviduct. The family is one of esjjecial 

 interest as exhibiting transitional characters, and it is thought to be allied to certain 

 fossil Isospondylous forms. 



But one species is now known. The trout perch {Percopsis guttatus) is a small, 

 silvery fish, reaching a length of about six inches. It is found in the great lakes and 

 their tributaries, and occasionally in the Mississijipi valley. At Chicago it abounds 

 about the wharves, where it is used as bait. 



Sub-Order IV. — HAPLOMI. 



The sub-order Haplomi is characterized, among the physostomous fishes, by the 

 absence of the prsscoi-acoid arch. In most other respects the group agrees technically 

 with the Isospondyli. There is never an adipose dorsal, and the rayed dorsal is more 

 or less j)osterior in position, often placed opposite to the anal. The head is depressed 

 above, and usually more or less scaly. The species are nearly all quite small in size, 

 and all inhabit fresh or brackish waters, some of them being found in nearly all parts 

 of the earth, with the exception of the Australian and Polynesian regions, and the 

 western parts of the United States. There are three families, all easily distinguished. 



The EsociD.E, or pikes, have the body long and slender, and the mouth large, its 

 bones armed with very strong, sharp teeth of different sizes, some of them being mov- 

 able. The upper jaw is not protractile, and its margin, as in the Salmonidte, is formed 

 by the maxillary. The scales are small, the dorsal fin far back and opposite the anal, 

 and the stomach is without pyloric coeca. There is but a single genus, with about 

 five species. Four of these are North American, the other one being found in Europe, 

 Asia, and North America. 



All the pikes are greedy and voracious fishes, very destructive to other species 

 which may happen to be their neighbors; "mere machines for the assimilation of 

 other organisms." Thoreau describes the pike as "the swiftest, wariest, and most 

 ravenous of fishes, which Josselyn calls the river wolf. It is a solemn, stately, rumi- 

 nant fish, lurking under the shadow of a lily-pad at noon, with still, circumspect, 

 voracious eye ; motionless as a jewel set in water, or moving slowly along to take up its 

 position ; darting from time to time at such unlucky fish or frog or insect as comes within 

 its range, and swallowing it at a gulp. Sometimes a striped snake, bound for greener 

 meadows across the stream, ends its undulatory progress in the same receptacle." 



