Se·la'chi·i noun plural [ New Latin , from Greek ......... a fish having cartilages instead of bones.] (Zoology) An order of elasmobranchs including the sharks and rays; the Plagiostomi. Called also Selacha , Selache , and Selachoidei . Found on http://www.encyclo.co.uk/webster/S/56
The Selachii (Selachians) are an order of Chondrichthyes. This order includes the sharks and the rays. They have numerous teeth which are replaced in rapid succession throughout life. Found on http://www.probertencyclopaedia.com/browse/BSA.HTM