Salagrams can be identified as different forms of the Lord according to Their natural shape and markings. The markings are all natural, as found at the Kali-Gandaki River.
This is a cool Salagram Sila. The teeth are drawn from Tilak. They wash off and are reapplied daily during the puja. However, He has natural tilak (which you can see between His conch-shell eyes (which are applied using beeswax), and a natural mouth.
Indradyumna Swami identified this Sila for me to be Shanta Nrsimha (peaceful Nrsimha, the half-man-half-lion incarnation of the Lord). Though He looks really fierce, He is actually in a very merciful mood.