Anatomical Features 



Perhaps the most outstanding ana- 

 tomical feature of many members of 

 the group is the wide expansion of the 

 pectoral fins, a feature which gives the 

 fish a disclike shape. The gill openings 

 are entirely on the ventral surface, with 

 no portion of them extending above the 

 plane of insertion of the pectoral fins. 

 The sharklike rays, including the saw- 

 fish and the guitarfish, are classified 

 as true rays on the basis of gill posi- 

 tion, certain differences in skeletal 

 structure which seem to more nearly 

 ally them to rays than to sharks, and a 

 few other, possibly more obscure, 

 characteristics. 



Several species of rays that inhabit 

 shallow water are provided with long, 

 sharp spines on the base of their tails. 

 These spines are capable of inflicting 

 serious injuries on persons coming in 

 contact with them. The seriousness of 



the -wound resulting from a ray- spine 

 puncture is apparently attributable to 

 secretion of poison in at least a fewr 

 instances, but is also due to the ac- 

 cumulated covering of dirt, slime, and 

 bacteria that clings to the spine, to the 

 configuration of the wound, and to the 

 jagged nature of the cut. Owing to the 

 deep-puncture character of the spine 

 wound, conditions are optimal for gan- 

 grene. 



Examination of the mouths and 

 tooth structure of rays and skates pro- 

 vides ready explanation of how some of 

 these creatures can feed upon hard- 

 shelled crustaceans and nriollusks. Un- 

 like the teath of most sharks, which are 

 pointed, sharp, and fitted for tearing, 

 the teeth of the typical rays and skates 

 are blunt, platelike, or arranged like a 

 pavement over the jaws and well- suited 

 for crushing. Jaw musculature is cor- 

 respondingly powerful. 



A 'Typical" r.iy, the roughtail stingray, Dasyatis centrouro. This specimen measured 62 inches across the fins and weighed 

 285 pounds. Such rays are taken frequently in trawl drags along the east coast of the United States. 



13 



