Microhydromys richardsoni Tate and Archbold, 1941 . Am. Mus. Novit., 1101:2.

TYPE LOCALITY: New Guinea, Irian Jaya, Idenburg River, 4 km SW Bernhard Camp, 850 m .

DISTRIBUTION: New Guinea; scattered localities in hill forest from type locality east to Sogeri in Port Moresby region (see map in Flannery, 19906:184).

COMMENTS: Known only by four specimens (Flannery, 1989). Distributional and biological data summarized by Flannery (1990b:184). Microhydromys richardsoni possesses the primitive pattern of the cephalic arterial circulation, a conformation shared with species of Crossomys, Hydromys, and Parahydromys, but not with Leptomys or the other genera of shrew mice ( Mayermys, Neohydromys, and Pseudohydromys).