276 LOWER VERTEBRATES. 



to one side. Tlie tendency to do so becomes more and more marked, but the eye of 

 the inclined side disdains to look downwards, and strives to turn upwards; the 

 endeavor accomplishes its purpose, and finally it becomes settled upwards, and the 

 contiguous parts of the skull are twisted round to correspond. 



The typical flat-fishes, constituting the family Pleuronectid^, are all much com- 

 pressed, with the contour more or less rhombiform ; the head is angulated at the 

 front, and generally the lower jaw is produced ; the preoperculum is quite distin- 

 guishable externally, and the mouth is oblique and rectilinear ; the lateral line is dis- 

 tinct. To it belong numerous species ; there are on the eastern coast of the United 

 States twenty-two species, and on the western coast twenty-four species. 



The most important representative of the family is the halibut {IIip2Mglossus 

 vulgaris) ; it is distinguished from all other species by its more elongated and much 

 thicker bod}', and its head is still thicker in proportion. The caudal fin is also 

 emarginate. It is the least aberrant of all the flat fishes, save one, of the American 

 waters. It is found in the northern Atlantic, as well as northern Pacific, very near 

 the shores in shallow water, and upon the off-shore banks and the edges of the conti- 

 nental slope down to a depth of two hundred to two hundred and fifty fathoms or 

 more. 



The halibut is emphatically a cold-water species. " That it ranges nine or ten 

 degrees farther south on the American • than on the European coast, is quite in 

 accordance with the general law of the distribution of fish life in the Atlantic ; indeed, 

 it is only in winter that halibut are known to approach the shore to the south of Cape 

 Cod, and it is safe to say that the temperature of the water in which they are at 

 present most frequently taken is never, or rarely, higher than 45°, and seldom higher 

 than 35°, and often in the neighborhood of 32°. Its geographic i-ange corresponds 

 closely to that of the cod-fish, with which it is almost invariably associated, though the 

 cod is less dependent upon the presence of very cold water, and in the western 

 Atlantic is found four or five degrees ^ — -in the eastern Atlantic at least two — nearer 

 the equator, while the range of the two species to the north is probably, though not 

 certainly, known to be limited relatively in about the same degree. In the same 

 manner the halibut appears to extend its wanderings further out to sea, and in deeper 

 and colder water than the cod. Although observations on this point have necessarily 

 been imperfect, it seems to be a fact that, while cod are very rarely found upon the 

 edge of the continental slope of North America, beyond the two hundred and fifty 

 fathom line, halibut are present there in abundance." 



The name halibut was formerly supposed to be derived from holy and but, that is, 

 a sacred or holy fl.at-fish ; but why it should have been called " holy " was a matter of 

 wonder, and the suspicion arose that something must be wrong in the etymology. 

 By far the most probable conjecture is, that it is descriptive of habitat, a word 

 meaning a hole flounder, or flat-fish living in holes or deep places; this would be 

 really apjaropriate as well as in accordance with usage in several languages. 



In Sweden it is called hallefisk or hfilleflundra, which means a hole-fish or hole 

 flounder; that is a deep-sea fish or deep-sea flounder. 



The halibut is the largest by odds of all the Pleuronectida^, and ranks indeed fourth 

 in size among the teleost fishes of the United States. There is, however, a consider- 

 able difference between the sexes. The male, it is claimed, rarely exceeds fifty 

 pounds, and is ordinarily in poor condition and less desirable for food. The aver- 

 age size of the full-a;rown female is somewhere between one hundred and one hun- 



