 There are well-developed skin flaps and grooves around the incurrent nostril opening, as well as a pair of grooves connecting them to the small, almost transverse mouth.The tooth rows number 32–34 in the upper jaw and 21–29 in the lower jaw; each tooth has an upright, awl-like central cusp and two lateral cusplets.The five pairs of gill slits are short, with the fourth and fifth pairs more closely spaced than the others.