Identifier: scienceguide7692amer (find matches)Title: Guide leafletYear: 1901 (1900s)Authors: American Museum of Natural HistorySubjects: American Museum of Natural History Natural historyPublisher: New York : The MuseumContributing Library: American Museum of Natural History LibraryDigitizing Sponsor: IMLS / LSTA / METROView Book Page: Book ViewerAbout This Book: Catalog EntryView All Images: All Images From Book Click here to view book online to see this illustration in context in a browseable online version of this book.Text Appearing Before Image:commercial leather known as ^galuchat isshark skin. Around the mouth of the shark, these denticles becomeenlarged and give rise to the teeth. The swifter sharks, like the Mackerel Shark (Case 11), pursue anddevour live fish, but the more sluggish ones, like the Nurse Shark arecontent with offal. Some with blunt teeth, like the Port Jackson Shark(Case 7), crush shellfish, while some with very large mouths and reducedteeth, such as the Whale Shark (see separate case) and the Basking Shark,(above Case 11), feed like whales on small copepods and other floating,shrimp-like forms. Reproduction: Sharks produce but a few eggs at a time, in contrastto the hundreds of thousands produced by a single Codfish; hence theycan afford, so to speak, to invest a large amount of capital in each egg,that is, to endow the young with a very large yolk. This nourishes theyoung for a long time, so that they are well equipped to take care of them-selves when they are hatched. In some sharks, however, the eggsText Appearing After Image:Fig;. 3. Evolution of the Bodj Form of Sharks. 10 THE WOhLI) OF FISHES 11 (levolop within tlic oviducts or (g«i; ducts, and tlic youn^ draw nourish-ment from the mother by means of root-hke outgrowths from the re^;ionof their gills. The Port Jackson Sharks (Heterodontidie). (Case 7;: Duringand before that ancient period of the earths history in which the vastswamps and forests of Pennsylvania were accumulating thcMr stores ofcoal-forming vegetation, the shallow seas of the world swarmed withancient sharks, many of which bore curved spikes on the front marginsof their fins. The more specialized forms of these early sharks becameextinct, but one family survives,—the Port Jackson Sharks—whichare still found living in the Pacific Ocean. These retain the stout finspines and whorl-like crushing teeth of their vastly distant ancestors.They lay eggs which are enclosed in a spirally twisted egg case. The Spined Dogfishes or Squaloid Sharks (Squalidae). (Case 7J:These sharks are far removeNote About Images 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 work.

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   + Selachimorpha

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