Fishes . e mouth, scales, and fin-spines of a premaxillary forms the entire edge of the upper jaw, themaxillary being without teeth. The air-bladder retains arudimentary duct. The bones of the head are full of mucouscavities, as in the European perch called Gymnocephalus andAcerina. There are two spines in the dorsal and one or twoin the anal, while the abdominal ventrals have each a spine andeight rays. Two species only are known among living fishes,these emphasizing more perfectly than any other known formsthe close relation really existing between spinous and soft-rayed forms. The
Fishes . e mouth, scales, and fin-spines of a premaxillary forms the entire edge of the upper jaw, themaxillary being without teeth. The air-bladder retains arudimentary duct. The bones of the head are full of mucouscavities, as in the European perch called Gymnocephalus andAcerina. There are two spines in the dorsal and one or twoin the anal, while the abdominal ventrals have each a spine andeight rays. Two species only are known among living fishes,these emphasizing more perfectly than any other known formsthe close relation really existing between spinous and soft-rayed forms. The single family of Percopsidce would seem tofind its place in Cretaceous rocks rather than in the waters of to-day. 456 Salmopercs and Other Transitional Groups 457 Percopsts guttata, the trout-perch or sand-roller of the GreatLakes, is a pale translucent fish with dark spots, reaching alength of six inches. It abounds in the Great Lakes and theirtributaries and is occasionally found in the Delaware, Ohio,. Fig. 361—Oregon Trout-perch, Columbia transmontana Eigenmann. Umatilla River, Oregon. Kansas, and other rivers and northwestward as far as Medi-cine Hat on the Saskatchewan. It is easily taken with a hookfrom the piers at Chicago. Columbia transmontana is another little fish of similar type,but rougher and more distinctly perch-like. It is found insandy or weedy lagoons throughout the lower basin of theColumbia, where it was first noticed by Dr. Eigenmann in 1892. Fig.
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