. Cold-blooded vertebrates: part I. Fishes. Fishes; Amphibians; Reptiles. THE STRUCTURE OF A FJSH As we have found in other features, a long; evolution- ary development of the skeleton is illustrated in fish forms now living. In the lancelets, which constitute the lowest type of fishes, the skeleton consists merely of a cartilagi- nous rod, or notochord, occupying the usual position of. Fig. 28. Crushing teeth of the black drum, Pogonias cromis, forming two pavements on the roof and floor of the mouth the backbone. Advancing to the most primitive of the fishes possessing a true spinal column,
. Cold-blooded vertebrates: part I. Fishes. Fishes; Amphibians; Reptiles. THE STRUCTURE OF A FJSH As we have found in other features, a long; evolution- ary development of the skeleton is illustrated in fish forms now living. In the lancelets, which constitute the lowest type of fishes, the skeleton consists merely of a cartilagi- nous rod, or notochord, occupying the usual position of. Fig. 28. Crushing teeth of the black drum, Pogonias cromis, forming two pavements on the roof and floor of the mouth the backbone. Advancing to the most primitive of the fishes possessing a true spinal column, namely the sharks, we find the skeleton still cartilaginous, though, of course, much more developed than in the lancelets. The same is true of the skates, lampreys, sturgeons, and a few other groups, and on this account they are, with the sharks, often referred to as cartilaginous fishes. Finally we come to the highest group possessing an ossified skeleton, known as bony fishes, or teleosts (Fig. 29). To this group all American common food fishes except the sturgeons belong. In a general way the fish skeleton corresponds to that of man and the other vertebrates, though details of structure are vastly different. The backbone is present, of course, and all except the lowest forms have a cranium. The higher fishes also possess some sort of shoulder girdle, to which the pectoral fins, corresponding to the arms in man, are attached. We see, furthermore, a gradual develop- [61I. 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 Hildebrand, Samuel F. (Samuel Frederick), 1883-1949; Gilmore, Charles Whitney, 1874-; Cochran, Doris M. (Doris Mable), 1898-1968. [New York, Smithsonian institution series, inc. ]
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Keywords: ., bookcentury1900, booksubj, booksubjectfishes, booksubjectreptiles
