The Sharks-Part Two 359 



This last family in the long shark line is linked with an ancient form 

 that swam in Jurassic seas. There is something oddly prehistoric about 

 the appearance of these bullheaded sharks that bear, before each dorsal 

 fin, a stout spine that resembles a horn; and indeed they are a most 

 archaic group anatomically. 



The Port Jackson shark {Heterodontiis portjacksoni Meyer, 1793) 

 of Australian waters belongs to this family, as does the Pacific Horned 

 shark {Heterodontiis francisci Girard, 1854), found from Alorro Bay 

 to Cape San Lucas, Lower California, and into the Gulf of California. 

 Some eight other species are found in the eastern Pacific, and off East 

 Africa and the East Indies. Horn sharks are not known in the Atlantic 

 or the Mediterranean. The Port Jackson shark is also called the Bullhead 

 and the Oyster Crusher (it lives on mollusks and crustaceans) in Australia. 

 In California, it is sometimes called the Pig shark because of its porcine 

 head. Horn sharks grow to about 4 feet. 



Horn sharks lay egg cases that are equipped with spiral flanges, 

 giving them a screw-like appearance. The egg cases, measuring about 

 4 by 2 inches, are sometimes eaten by female Horn sharks. And, to com- 

 plete the cannibalism, Horn sharks are sometimes eaten by Tiger sharks 

 (Galeocerdo cuvieri). 



THE COMPANIONS OF THE SHARK 



Two bony fish— the remora and the pilot fish— are closely associated 

 with many species of Selachians. Though these fish are not related to 

 any Selachians, and are true Teleosts, they are included here because 

 they are often found with Selachians. 



The big shark is often the host of a colony of followers, some of 

 them freeloaders at the shark's meals. These vagabonds— remoras and 

 pilot fish— are apparently never molested by the shark, and they do not 

 seem to do anything for the shark, to earn their immunity. 



Instead, they eat the crumbs that drop when the shark, a coarse 

 feeder, dines. The coexistence of the shark and its smaller companions is 

 called comnie7isalism—\\ier2i\\y, eating from the same table. 



The Remora (Family Eche?7eidae), or Sucker Fish, is a fish of ancient 

 legend. The Greeks called it the "ship-holder," and its present-day name 

 comes from a Latin word meaning "a delay." The historian Pliny said 

 that the Emperor Caligula was fatally delayed on his voyage to Antium 

 by remoras, which held his ship despite 400 oarsmen's efforts to free it. 

 Alark Antony's defeat at Actium was blamed on remoras that kept his 

 ship fast when Antony ordered it into battle. We also have it on the 

 word of Ben Jonson that a remora can "stay a ship that's under sail." 



