 The head is large and triangular , while the neck is greatly narrowed : almost one @-@ third the width of the head . A pair of " horns " is present between the raised nostrils — tiny in B. g. gabonica , but much larger in B. g. rhinoceros . The eyes are large and <unk> , set well forward , and surrounded by 15 – 21 <unk> scales . There are 12 – 16 <unk> scales across the top of the head . Four or five scale rows separate the <unk> and the <unk> . There are 13 – 18 <unk> and 16 – 22 <unk> . The fangs may reach a length of 55 millimetres ( 2 @.@ 2 in ) : the longest of any venomous snake . 
