. Fishes. Fishes. CHAPTER XXIX SALMOPERC^ AND OTHER TRANSITIONAL GROUPS UBORDER Salmopercae, the Trout-perches: Percopsidae. —More ancient than the Hemibranchii, and still more distinctly in the line of transition from soft-rayed to spiny-rayed fishes, is the small suborder of Salmopercas. This is characterized by the presence of the adipose fin of the salmon,. Fig. 360.—Sand-roller, Pecropsis gutlatus Agassiz. Okoboji Lake, la. in connection with the mouth, scales, and fin-spines of a perch. The premaxillary forms the entire edge of the upper jaw, the maxillary being without teeth. The air-bl
. Fishes. Fishes. CHAPTER XXIX SALMOPERC^ AND OTHER TRANSITIONAL GROUPS UBORDER Salmopercae, the Trout-perches: Percopsidae. —More ancient than the Hemibranchii, and still more distinctly in the line of transition from soft-rayed to spiny-rayed fishes, is the small suborder of Salmopercas. This is characterized by the presence of the adipose fin of the salmon,. Fig. 360.—Sand-roller, Pecropsis gutlatus Agassiz. Okoboji Lake, la. in connection with the mouth, scales, and fin-spines of a perch. The premaxillary forms the entire edge of the upper jaw, the maxillary being without teeth. The air-bladder retains a rudimentary duct. The bones of the head are full of mucous cavities, as in the European perch called Gymnocephalus and Acerina. There are two spines in the dorsal and one or two in the anal, while the abdominal ventrals have each a spine and eight rays. Two species only are known among living fishes, these emphasizing more perfectly than any other known forms the close relation really existing between spinous and soft- rayed forms. The single family of Percopsidce would seem to find its place in Cretaceous rocks rather than in the waters of to-day. 456. 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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