The True Sharks 557 



and Pteroplatea altavela, in Europe. They are all very much 

 alike, olive, with the brown upper surface pleasingly mottled 

 and spotted. 



Sting-rays of various types, T&niura, Urolophus, etc., occur 

 as fossils from the Eocene onward. A complete skeleton called 

 Xiphotrygon acutidens, distinguished from Dasyatis by its 

 sharp teeth, is described by Cope from the Eocene of Twin Creek 

 in Wyoming. Vertebrae of Urolophus are found in German Eocene. 

 Cyclobatis (oligodactylus] , allied to Urolophus, with a few long 

 pectoral rays greatly produced, extending over the tail and 

 forming a rayed wreath-like projection over the snout, is known 

 from the Lower Cretaceous. 



Myliobatidae. -- The eagle-rays, Mylicbatid& t have the pec- 

 toral fins extended to the snout, where they form a sort of rayed 

 pad. The teeth are very large, flat, and laid in mosaic. The 

 whip-like tail is much like that in the Dasyatida, but the spine 

 is usually smaller. The eagle-like appearance is suggested 

 by the form of the skull. The eyes are on the side of the head 

 with heavy eyebrows above them. The species are destructive 

 to clams and oysters, crushing them with their strong flat teeth. 



In Aetobatus the teeth are very large, forming but one row. 

 The species Aetobatus narinari is showily colored, brown with 

 yellow spots, the body very angular, with long whip-like tail. 

 It is found from Brazil to Hawaii and is rather common. 



In Myliobatis the teeth are in several series. The species 

 are many, and found in all warm seas. Myliobatis aquila is 

 the eagle-ray of Europe, Myliobatis calif ornicus is the batfish of 

 California, and Myliobatis tobijei takes its place in Japan. 



In Rhinoptera the snout is notched and cross-notched in 

 front so that it appears as if ending in four lobes at the tip. 

 These "cow-nosed rays," or " whipparees," root up the soft 

 bottoms of shallow bays in their search for clams, much as a 

 drove of hogs would do it. The common American species 

 is Rhinopterus bonasus, Rhinoptera steindachneri lives in the 

 Gulf of California. 



Teeth and spines of all these genera are common as fossils 

 from the Eocene onwards, as well as many of the extinct genus, 

 Ptychodus, with cyclospondylous vertebrae. Ptychodus mam- 

 milaris, rugosus, and decurrens are characteristic of the Creta- 



