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Table of Contents

This family, which includes a large number of species in tropical and temperate seas, is characterized by a head of normal shape, eye with a nictitating (winking) membrane, tail with the upper lobe considerably larger than the lower but not very long, 2 spineless dorsal fins, the first usually much larger than the second in most of the Atlantic species,[85] an anal fin, a caudal peduncle lacking lateral keels, and sharp, bladelike teeth with a single cusp. All bear "living" young; [page 37] some have a placental connection between mother and embryo, but others do not.

[85] The lemon shark (Negaprion brevirosuris) of warmer waters, which has been known to stray to New Jersey, is an exception in this respect; its second dorsal is nearly as large as its first dorsal.