The Vitarka mudra is the gesture of discussion and transmission of Buddhist teaching.
The Vitarka mudra is done by joining the tips of the thumb and the index together, and keeping the other fingers straight very much like Abhaya and Varada mudra but with the thumbs touching the index fingers.
The Vitarka mudra has a great number of variants in Mahayana Buddhism in East Asia. In Tibet it is the mystic gesture of Taras and Bodhisattvas with some differences by the deities in Yab-yum. (Vitarka mudra is also known as Prajnalinganabhinaya or Vyakhyana mudra (mudra of explanation).
(Japanese: Seppo-in, An-i-in; Chinese: Anwei Yin).