Selachians Extraordinary 263 



wholly fresh waters, in some cases thousands of miles from the sea. They 

 are found living over great depths of the oceans. And they are distributed 

 along the shelves of all the Continents. Their temperature range and 

 salinity requirements seem to have been compensated for in their long 

 evolutionary history. 



Seen on the sea bottom, a ray appears to be an inert shape whose only 

 movement is the persistent blinking of two odd, oblong objects that look 

 like eves: the spiracles. 



But the ray is a creature of illusion. It does not always sprawl on 

 the bottom; it often hovers, moves slowly, or even "flies" along, with its 

 wing-like pectoral fins flapping like a bird, touching the sand or silt and 

 fanning small crustaceans, starfish, and other food off^ the bottom so 

 that they can be more easily eaten. Its eyes and spiracles are on the top 

 of its body, and it is the spiracles, pulsating with each intake of breath, 

 that appear to be blinking eyes. Its real eyes, ever looking up, never see 

 bottom— and never blink. 



All appearances of sluggishness vanish instantly when a ray suddenly 

 sweeps up from the bottom and glides through the darkening sea, un- 

 dulating its pectoral fins in an exquisite sequence of motions as graceful 

 as the flutter of a silken veil in a gentle wind. 



Rays resemble skates, but several rather technical diff^erences set the 

 two apart in the phylogenetic family tree of the Selachians. Among 

 fishermen and non-experts, the two are often synonymous. Even their 

 names are from the same root. Skate is a Norse word. The creatures the 

 Norse called skates were christened rays (raie) by the French, ray 

 meaning striped or streaked, a characteristic which doesn't apply to all 

 species.^ One way to difi^erentiate them is to remember that skates, es- 

 pecially those commonly seen in North America, are generally long- 

 nosed and rays are generally not long-nosed. But this is a very loose 

 generalization with plentiful exceptions. 



There is another difi^erence between skates and rays, a diflFerence more 

 elemental than ichthyological classifications: as far as is known, skates 

 are harmless. But some rays exist with most fearsome defenses. 



Unlike the skates, which produce their young oviparously in egg 

 cases, the rays are all believed to be ovoviviparous, bringing forth their 

 young alive (after they have hatched from eggs within the mother). 

 In some rays, there is a connection between the mother and the uterine- 

 hatched embryo that is more direct than is found in ovoviviparous sharks. 

 The female rays of this type have a uterus whose walls are densely lined 

 with long filaments, called villi. The villi, passing into the spiracles of 



^ The "striping" actually referred to the many "raies" disclosed in the fin when 

 served as a table delicacy which has been popular in France since time immemorial. 



