<prompt> An arrow mark or bird foot mark on the centre of head suggest it isPit viperSaw scaled viperKing cobraKrait  <response>: If the head is triangular and covered with small scales, it may be poisonousviper. If there is an arrow mark or bird foot mark on the centre of the head, it is poisonous saw scaled viper Ref: FORENSIC MEDICINE AND TOXICOLOGY Dr PC IGNATIUS THIRD EDITION PAGE 511 