XVII ELASMOBRANCHII—SELACHII 447 
Indian Ocean attains a leneth 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 he on the bottom watching for their 
prey, and in accordance with this habit their coloration closely 
resembles that of their surroundings.’ A large North Atlantic 
Shark (Psewdotriakis microdon), of which only two specimens are 
Fic. 254.—A female Dog-Fish (Seyllivm canescens), from the south-western coast of 
: South America. (From Giinther. ) 
known, one taken on the Portuguese coast, and the other, 10 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, Scylliwm 
(Scylliorhinus) profundorum having been obtained from a depth 
of 816 fathoms in the North Atlantic? 
Most of the fossil Seylliidae 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 Seylliwm, and Pris- 
tiurus, are found, nearly complete. Scylliwm 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. 328. 2 Goode and Bean, op. cit. p. 23. 
