This is a pictograph of a mugger crocodile. It is both the singular and plural form of the compound noun mugger crocodile.
Illustrative Text Reference:
Mohenjo-daro: Seal: The Schoyen Collection: Schoyen Reference: MS 5059: (A note on the Schoyen website says that this seal inscription wil be published in Volume 3 of the Corpus of Indus Seals
and Inscriptions.): https://www.schoyencollection.com/palaeography-collection-introduction/early-writing-introduction/4-1-4-indus-valley/indus-valley-seal-ms-5059: Accessed: 25 February 2018.