172 



UNDERWATER GUIDE TO MARINE LIFE 



the northern sting ray south of Cape Hatteras and these two rays are very 

 similar in habits. It is easily recognized by the finlike folds under the tail behind 

 the spine, a keel above this fold on the tail, and the angular shape of the 

 pectorals. It averages three feet across the pectorals and probably reaches 4 feet. 

 It often enters very shallow water, at which times the pectoral fins and tail 

 may break the surface. 



The northern sting ray, Dasyatis centrura, reaches 13 to 14 feet in length 

 and 5 feet in breadth. At Wz feet in breadth, it weighs 180 pounds. It is much 

 like the southern sting ray but has a thorny tail with no keel on top of the tail. 

 It is locally plentiful in shallow waters from Cape Hatteras to Cape Cod. 



The diamond sting ray, Dasyatis dipteninis, is much like the preceding 

 species. It is found from British Columbia to Central America and is common 

 in bays from San Diego southward. It reaches a length of 6 feet. 



Fig. 78. Butterfly ray. 



BUTTERFLY RAY (sAND skate) : Gyuinura viicTiira . 



Size: Averages 2 feet in breadth. To 4V2 feet across, rarely. 



Distribution: From Massachusetts to Brazil. Most common from the Gulf of 

 Mexico to the Chesapeake. 



Identification: The breadth is much greater than the length, and the spineless 

 tail is very short. The color is gray, brown, or even greenish or purplish. It can 

 change its color to match the surroundings somewhat. 



Habits: This ray behaves much like the Dasyatis species, but is more active, 

 especially in response to tide changes. This ray prefers coastal sandy bottoms 

 and feeds on a wide variety of molluscs and crustaceans. It may enter brackish 

 waters. It bears young from May to August. 



Similar Species: The giant butterfly ray, GyMiniira altavela, grows to a 

 breadth of 7 feet or more. It is found from Massachusetts to Brazil. This ray has 

 small spines on the tail base. It is known to utter a grunting sound when in 

 distress. 



The butterfly sting ray, Gymnura marmorata, of Point Conception to Mazat- 

 Ian, has a small sting and reaches a breadth of 5 feet. It is common in shallow 

 bays along beaches. 



