الفهرس 
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Abstract
Elasmobranchs have existed since the Upper Devonian and constituted a diverse group that has been classified in several different ways. These fishes have cartilaginous endoskeletons that are often hardened by calcifications.
Among elasmobranchs, skates and rays are recognized by a depressiform body, with the pectoral fins extending forward and fusing to the head so that the five pairs of gill openings are located ventrally.
Fishes of Family Rhinobatidae are of rather shark- like fishes and generally referred to as guitarfishes. The name is apparently based upon the appearance given by the flattened head, pectoral fins, and snout, followed by the tapering body and tail.
Taxonomical and biological studies on the cartilaginous fishes of the Northwestern Atlantic were done by Bigelow and Schroeder (1953). On the other hand Gunther (1870), Le Danois (1913) and Wheeler (1969) studied the taxonomy and some biological characters of hypotremata in the Northeastern side of the Atlantic (British Isles and European coasts). Similar studies on.