xvii ELASMOBRANCHII SELACHII 447 



Indian Ocean attains a length of 10 to 15 feet, and is remark- 

 able for its handsome coloration of dark bands on a yellow 

 ground, which has suggested the name of Tiger- or Zebra-Shark. 

 The pelagic genus Ginglymostoma has the terminal portion of the 

 tail bent upwards, and grows to a length of 6 to 12 feet. It is 

 represented by species in the Indian Ocean and the tropical 

 parts of the Atlantic (West Indies and the west coast of Mexico). 

 Crossorhinus includes species of large size, some of which are 

 10 feet long. They are ground-sharks, frequenting the coasts of 

 Australia and Japan, which lie on the bottom watching for their 

 prey, and in accordance with this habit their coloration closely 

 resembles that of their surroundings. 1 A large North Atlantic 

 Shark (Pseudotriakis microdon), of which only two specimens are 



FIG. 254. A female Dog-Fish (Scyllium canescens), from the south-western coast of 

 South America. (From Guiither. ) 



known, one taken on the Portuguese coast, and the other, 1 feet 

 in length, off Long Island, on the Atlantic coast of North 

 America, has the general characters of the Scylliidae, except that 

 the first dorsal fin is opposite the interval between the pectoral 

 and pelvic fins. Some Scylliidae live at great depths, Scyllimn 

 (Scyllwrhinus) profundorum having been obtained from a depth 

 of 816 fathoms in the North Atlantic. 2 



Most of the fossil Scylliidae belong to existing genera. The 

 earliest known representatives of the family occur in the Upper 

 Jurassic (Lithographic Stone of Bavaria), where the extinct genus 

 Palaeoscyllium, a near ally of the existing Scyllium, and Pris- 

 tiurus, are found, nearly complete. Scyllium itself ranges from 

 the Cretaceous through the different Tertiary formations. A 

 species of Chiloscyllium has been recorded from the Miocene 

 Tertiaries, and detached teeth of Ginglymostoma from the Eocene 

 of Belgium and North America. An extinct genus (Mesiteia), 

 which is found in the Upper Chalk of Mount Lebanon and the 

 Upper Eocene of Monte Bolca, is remarkable for the enclosure of 



1 Giinther, Study of Fishes, p. 323. 2 Goode and Bean, op. cit. p. 23. 



