 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 moveable , set well forward , and surrounded by 15 – 21 circumorbital scales . There are 12 – 16 interocular scales across the top of the head . Four or five scale rows separate the suboculars and the supralabials . There are 13 – 18 supralabials and 16 – 22 sublabials . The fangs may reach a length of 55 millimetres ( 2 @.@ 2 in ) : the longest of any venomous snake . 
 The head <a href='drop_aux' title='1'><mark>is</mark></a>large and triangular , while the neck is greatly narrowed : almost one @-@ third the width of the head . A pair of " horns " <a href='drop_aux' title='2'><mark>is</mark></a>present between the raised nostrils <a href='null_genetive' title='3'><mark>—</mark></a>tiny in B. g. gabonica , but much larger in B. g. rhinoceros . The eyes <a href='drop_aux' title='4'><mark>are</mark></a>large and moveable , set well forward , and surrounded by 15 – 21 circumorbital scales . <a href='dey_it' title='5'><mark>There</mark></a> are 12 – 16 interocular scales across the top of the head . Four or five scale rows separate the suboculars and the supralabials . <a href='dey_it' title='6'><mark>There</mark></a> are 13 – 18 supralabials and 16 – 22 sublabials . The fangs may reach a length of 55 millimetres ( 2 @.@ 2 in ) : the longest of any venomous snake . 
Da head large and triangular , while tdaneck is greatly narrowed : almost one @-@ third thdaidth of the head . A pair of " horns " present between thedaised nostrils  tiny in B. g. gabonica , but much larger in B. g. rhinoceros . The das bigass and moveable , set well forward , and surrounded by 15 – 21 circumorbital scales . It is 12 – 16 interocular scales across the top of the hda . 4 or five scale rows separate the suboculars and the sudalabials . It is 13 – 18 supralabials and 16 – 22 sublabials . The fangs may reach a length of 55 millimetres ( 2 @.@ 2 in ) : the longest of any venomous snake .