 The pectoral fin disc of the porcupine ray is evenly oval , almost as wide as long , and very thick at the center , giving it a domed appearance . The tip of the snout is rounded and barely protruding . The small eyes are closely followed by much larger spiracles . Between the narrow nostrils is a skirt @-@ shaped curtain of skin ; the posterior margin of the curtain is strongly fringed and overhangs the mouth . The mouth bears 3 – 5 papillae on the floor and prominent furrows at the corners . The area around the mouth , including the curtain , are heavily covered by more papillae . There are around 48 tooth rows in either jaw . The teeth are small and flattened . Five pairs of gill slits are located on the underside of the disc . 
