Distinguished from all other sharks by the enormous gill slits practically encircling the head; dermal denticle gill rakers; pointed snout; huge, sub terminal mouth with minute hooked teeth; caudal peduncle with strong lateral keels, and lunate caudal fin. Body covered with placoid scales. Blackish to grey-brown, grey, or blue-grey, often with irregular white blotches under the head and abdomen (Ref. 43278). Also Ref. 309, 5983.