Abstract
A name Desmostylus mirabilis nov. is proposed for the remain recently acquired from a tributary of the Keton-gawa in Japanese Saghalin, which, the writer thinks, represents a species distinct from D. hesperus MARSH and D. japonicus TOKIJNAGA and IWASAKI, the two well established species of the genus. It has a much larger skull with a narrower parietal region and a smaller internoanterior column ofthe last upper premolar than the Oregon form and differs from D. japonicus in being provided with a broader M2 and a smaller P4 in the upper jaw and a broader M2 in the lower. The columns of the lower M2 are in the new species 7 in number instead of being 6 and those of the upper M3 seem to be less slender.
