Chinese Mysterysnail
Viviparus malleatus 
Japanese Mysterysnail
V. japonicus
The Chinese mysterysnail (Viviparus malleatus) and The Japanese mysterysnail (V. japonicus) are two very similar species.  Both introduced species are larger than the native species and their shells lack the color banding typical of native species.  They have a smooth shell that is thin in structure, but strong. Color is uniform, light to dark olive-green, without any color bands.  These snails can usually be found partially buried in the mud or silt of lakes, ponds, irrigation canals, and roadside ditches or slow streams.  They prefer quiet water where there is some vegetation and a mud bottom.  A large Chinese mysterysnail can reach 65mm in length with 6 or 7 whorls on their shells.  This species is native to Burma, Thailand, South Vietnam, China, Korea, and Asiatic Russia in the Amur region, Japan, the Philippines, and Java.  It is suspected that introduction into the United States was from accidental or intentional releases from the aquarium industry.