Abstract
Two new species and two morphological variant taxa of sessile rotifers found during a survey of Thai rotifers are reported upon. Living specimens were collected and identified from twelve sampling sites. The specimens were photographed, and prepared for SEMs of dorsal plates and trophi. Two new species of genus Limnias are recognized. Limniaslenis sp. n. possesses a corona with a relatively shallow ventral sinus, and a dorsal plate without any projection, whereas Limniasnovemceras sp. n. carries a corona with a deep and wide ventral sinus, and a dorsal plate with nine projections. Two morphological variants of Limniasmelicerta are discussed, which are designated as L.melicerta SH and L.melicerta LH on the basis of the length of the horns on their dorsal plates. Moreover, both a dichotomous key and a formula key are provide including all Limnias species known to date.