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.
Indradyumna Swami told me during a recent visit that this was a very, very auspicious (and angry!) Salagram Sila known as Varaha-Nrsimha. On the left of His face (right of the picture) is the tusk of Varaha. In the center is the mouth of Nrsimha.