 Rather heavily built , the bignose shark has a long , broad , and blunt snout with the nostrils preceded by well @-@ developed , triangular flaps of skin . The moderately large , circular eyes are equipped with nictitating membranes ( protective third eyelids ) . The mouth is broadly curved and lacks obvious furrows at the corners . The upper teeth number 14 – 16 rows on either side and have tall , broad , triangular cusps with serrated edges ; they are erect at the jaw center and become increasingly oblique towards the sides . The lower teeth number 14 – 15 rows on either side and have narrow , erect cusps with extremely fine serrations . The five pairs of gill slits are moderately long . 
