. Animal biology. Zoology; Biology. 348 METAZOAN PHYLA and also more primitive than any other known fishes, either Uving or extinct. They had a terminal mouth instead of a ventral one. The eggs were probably fertilized externally, since the male had no claspers. In them also the notochord persisted as a continuous rod, the vertebral column being little more developed than that of the cyclostomes. Their characteristics seem to point to a primitive fish ancestor which had an. Spirac/e ' • . KlSyi'*, r Fig. 244.—Common skate, Raja erinacea Mitchill. X {Redrawn from Jordan ''Guide to the Study of
. Animal biology. Zoology; Biology. 348 METAZOAN PHYLA and also more primitive than any other known fishes, either Uving or extinct. They had a terminal mouth instead of a ventral one. The eggs were probably fertilized externally, since the male had no claspers. In them also the notochord persisted as a continuous rod, the vertebral column being little more developed than that of the cyclostomes. Their characteristics seem to point to a primitive fish ancestor which had an. Spirac/e ' • . KlSyi'*, r Fig. 244.—Common skate, Raja erinacea Mitchill. X {Redrawn from Jordan ''Guide to the Study of Fishes " by the courtesy of D. Appleton & Company.) elongated spindle-shaped body, a mouth armed with dermal teeth, a greater number of gill shts than in any existing forms, paired fins, and a diphycercal tail fin made up of a single lobe. 368. Economic Facts.—Sharks have always been feared by man and undoubtedly at times they will attack human beings in the water. They are, however, less likely to do so than is generally supposed. One of the dogfish sharks found on the Atlantic coast is an important enemy of the lobster, and a second devours large numbers of valuable food fish. It is stated that the spined dogfish shark, Squalus acanthias. 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 Wolcott, Robert Henry, 1868-1934; University of Nebraska (Lincoln campus). Dept. of Zoology. New York ; London : McGraw-Hill Book Company, Inc.
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