The largest of the clown beetles on the sandy beach, N. sulcifrons is easily distinguished. They are between 7.0mm and 8.0mm, with all black bodies and a golden iridescence present on their cuticle and arced grooved along its elytra. Their appendages are spiny and will be tucked into their body when disturbed. They can be found in similar kelp wrack as the other clown beetles, favoring dryer kelp, which they may feed on. Not many predators are likely to penetrate their defenses, including a bitter, milky substance to counteract predation.