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THE SUBCLASS PARAPSIDA
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Family Mesosauridae. Lower Permian. Stereosternum Cope (Notosaurus Marsh), Mesosaurus Gervais, Brazil. Mesosaurus Gervais (Ditrichosauruus Gurich), ? Noteosaurus Broom, South Africa.
Fig. 176. Restoration of Mesosaurus. After McGregor. The posture of the hind leg is slightly modified.
9. ORDER ICHTHYOSAURIA
Marine reptiles with all aquatic adaptations of the tail-propelling type: elongated face; posterior nares, sclerotic plates, short neck, elongated body, no sacrum, long, flattened or dilated tail, short pro-
