. Catalog of fossil fishes in the Carnegie Museum. Fishes, Fossil. 322 MEMOIRS OF THE CARNEGIE MUSEUM. Gymnarchus, through Mormyrus, up to the extremely specialized organ of Gnatho- nemus. Progressive stages in the elongation of the rostrum in scombroid fishes have been pointed out by Regan. The structural changes which have attended the formation of a beak are illustrated in the following diagrams:. Fig. 1. Diagram showing the structure of the rostrum in Acanthocybium (a), Histiophorus (b), Xiphias (c), and Xiphiorhynchus (d). pmx, praemaxillary; mx, maxillary; na, nasal; eth, ethmoid; fr, fr
. Catalog of fossil fishes in the Carnegie Museum. Fishes, Fossil. 322 MEMOIRS OF THE CARNEGIE MUSEUM. Gymnarchus, through Mormyrus, up to the extremely specialized organ of Gnatho- nemus. Progressive stages in the elongation of the rostrum in scombroid fishes have been pointed out by Regan. The structural changes which have attended the formation of a beak are illustrated in the following diagrams:. Fig. 1. Diagram showing the structure of the rostrum in Acanthocybium (a), Histiophorus (b), Xiphias (c), and Xiphiorhynchus (d). pmx, praemaxillary; mx, maxillary; na, nasal; eth, ethmoid; fr, frontal. (After C. T. Regan, Ann. & Mag. Nat. Hist. (8), Vol. Ill, 1909, p. 73). No attempt has ever been made, so far as the present writer is aware, to explain by what means or processes the gradual formation of a rostral beak has been brought about. An interesting theory, however, has been advanced by Dr. Gregory to explain the progressive elongation of the pre-orbital region in the Sjoignathidse to form a tubiform snout with terminal jaws. The explanation given is as foUows:. 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 Eastman, Charles Rochester, 1868-1918; Carnegie Museum. Pittsburgh : Published by the authority of the Board of Trustees of the Carnegie Institute
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