. Fishes. Fishes. 696 Suborder Heterosomata always provided with teeth. Among the 500 species of flounders is found the greatest variation in size, ranging in weight from an ounce to 500 pounds. The species found in arctic regions are most degenerate and these have the largest number of ver- tebras and of fin-rays. The halibut has 50 vertebras (16 +S4), the craig-flounder 58, while in Etropus and other tropical forms the number is but 34 (10-I-24). The common flounders of intermediate geographical range (Paralichthys dentatus, etc.) show intermediate numbers as 40 (10 +30).. Ftr,. 600. Fki. 60
. Fishes. Fishes. 696 Suborder Heterosomata always provided with teeth. Among the 500 species of flounders is found the greatest variation in size, ranging in weight from an ounce to 500 pounds. The species found in arctic regions are most degenerate and these have the largest number of ver- tebras and of fin-rays. The halibut has 50 vertebras (16 +S4), the craig-flounder 58, while in Etropus and other tropical forms the number is but 34 (10-I-24). The common flounders of intermediate geographical range (Paralichthys dentatus, etc.) show intermediate numbers as 40 (10 +30).. Ftr,. 600. Fki. 601. Fig. 600.—Heterocercal tail of young Trout, Salmo jario LiuiuT'us. (After Parker & Has well.) Fig. tOl —Homocercal tail of a Flounder, Paralichthys calijornicus. It is, perhaps, related to the greater pressure of natural selection in the tropics, showing itself in the better differentiation of the bones and consequently smaller number of the vertebrse. Fossil flounders are very few and give no clue as to the origin of the group. In the Eocene and Miocene are remains which have been referred to Bothus (Rhombus). Bothns minimus is the oldest species known, described by Agassiz from the Eocene of Monte Bolca. In the Miocene are numerous other species of Bothus, as also tubercles referable to Scophthalmus. On the testimony of fossils alone the genus Bothus, or one. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Jordan, David Starr, 1851-1931. New York, H. Holt and Company
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