. A civic biology : presented in problems. Biology; Sanitation. ANIMALS CLASSIFIED 1X7 secreting mucus, a slimy substance which helps them go through the water easily. They usually lay very many eggs. CLASSIFICATION OF FISHES ORDER I. The Elasmobranchs, Fishes which have a soft skeleton made of cartilage and exposed gill slits. Examples : sharks, skates, and rays. ORDER II. The Ganoids. Fishes which once were very numerous on the earth, but which are now almost extinct. They are protected by platelike scales. Ex- amples : gars, sturgeon, and bowfin. ORDER III. The Teleosts, or Bony Fishes. The
. A civic biology : presented in problems. Biology; Sanitation. ANIMALS CLASSIFIED 1X7 secreting mucus, a slimy substance which helps them go through the water easily. They usually lay very many eggs. CLASSIFICATION OF FISHES ORDER I. The Elasmobranchs, Fishes which have a soft skeleton made of cartilage and exposed gill slits. Examples : sharks, skates, and rays. ORDER II. The Ganoids. Fishes which once were very numerous on the earth, but which are now almost extinct. They are protected by platelike scales. Ex- amples : gars, sturgeon, and bowfin. ORDER III. The Teleosts, or Bony Fishes. They compose 95 per cent of all living fishes. In this group the skeleton is bony, the gills are protected by an operculum, and the eggs are numerous. Most of our common food fishes belong to this class. ORDER IV. The Dipnoi, or Lung Fishes. This is a very small group. In many A bony fish. respects they are more like amphibians than fishes, the swim bladder being used as a lung. They live in tropical Africa, South America, and Australia, inhabiting the rivers and lakes there. Characteristics of Amphibia. - The frog belongs to the class of vertebrates known as Amphibia. As the name indicates (amphi, both, and bia, life), members of this group live both in water and on land. In the earlier stages of their development they take oxygen into the blood by means of gills. When adult, however, they breathe by means of lungs. At all times, but especially during the winter, the skin serves as a breathing organ. The. 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 Hunter, George W. (George William), 1873-1948. New York : American Book Company
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