The pelagic mollusk Cardiapoda placenta(Lesson,1830) is an uncommon species in China seas,which is unlisted in "Marine Species and Their Distribution in China(revised edition)" and "Checklist of Marine Biota of China Seas".The morphology of C.placenta was described and illustrated based on a single juvenile male specimen collected in the southern Taiwan Strait on 14 July 2005.In addition,the differences between the specimen collected and C.richardi Vayssiere,1903 were discussed.