Photographs of Yininemertes pratensis (Sun and Lu, 1998) taken in life. A A haul of a glass-eel net at the Han River Estuary, South Korea, on 6 April 2015 B magnification of a swarm of the same worms as in A from the Han River Estuary taken in the laboratory; arrow heads indicating the characteristic transverse narrow rings in the intestinal region C a specimen dug from clayey mud sediment with vegetation at Bailonggang in the Yangtze River Estuary, China, May 13, 2016 D a specimen dug from non-vegetated clay sediment at Chongming Island in the Yangtze River Estuary, China, 14 May 2016 E topotype from the Yangtze River Estuary showing an overview of whole specimen F topotype from China showing magnification of head, ventral view G topotype from China, magnification of intestinal region, showing the characteristic narrow transverse rings, indicated by arrow heads.