A description is given of the shell, renal organ, reproductive system and radula of topotypic specimens of Lymnaea cousini Jousseaume, 1887. A diagnosis between it and four other lymnaeids which also occur in South America and were previously studied by the author (L. columella, L. diaphana, L. viatrix and L. rupestris) is presented.
Lymnaea cousini; Lymnaea columella; Lymnaea diaphana; Lymnaea viatrix; Lymnaea rupestris; morphology; taxonomy; Ecuador