Baiomys is the genus of New World pygmy mice. Together with Scotinomys, it forms the tribe Baiomyini. It currently contains two extant species:
Southern pygmy mouse, Baiomys musculus
Northern pygmy mouse, Baiomys taylori
References
Amman, B R., R. D. Bradley. 2003. Molecular evolution in Baiomys (Rodentia: Sigmodontinae): Evidence for a genetic subdivision in B. musculus. Journal of Mammalogy 85:162-166.