Mudras are basically of two types - Asamyukta Hasta (or Asamyuta) (Single Hand Gestures) and Samyukta Hasta (or Samyuta) (Double Hand Gestures) Asamyukta Hasta (read: Uh-sum-yook-tha Husstha) - It is done using a single hand. The Natyashastra mentions 28 Mudras. There are four new Mudras added to this list. These Hand Gestures are a Part of Angika Abhinaya.
Image Plate from Owen Jones' 1853 classic, "The Grammar of Ornament".
_207, 1/31/05, 3:20 PM, 16C, 3062x4192 (568+411), 62%, Default Settin, 1/40 s, R74.2, G58.2, B73.3