Proteroglyphous snakes ("forward grooved") have shortened maxillae bearing few teeth except for a substantially enlarged fang pointing downwards and completely folded around the venom channel, forming a hollow needle. Because the fangs are only a fraction of an inch long in even the largest species these snakes must hang on, at least momentarily, as they inject their venom. Some spitting cobras have modified fang tips allowing them to spray venom at an attacker's eyes. This form of dentition is unique to elapids.