Some time ago I made a post about the subgenus Plekocheilus (Sparnotion) Pilsbry, 1944, with the type species P. (S.) hauxwelli (Crosse, 1872) as sole representative. At that time only one specimen was known from this taxon.
Thanks to Graham Oliver I was able to see another specimen, which he encountered in the Linter collection. Although the locality simply states “Peru”, there is no doubt about its identification. Compared to the paratype in the Museum of Comparative Zoology, Cambridge (Mass.), this specimen has all characteristics that were present in the lost holotype.
Although there seems a strange twist with this species, sharing most characteristics with Plekocheilus (Eudolichotis) and one—finely zigzag hydrophanous lines on the surface—with Plekocheilus (Aeropictus), I still feel this insufficient for recognizing a separate, monotypic subgenus for this species. So I stick to my conclusion “based on the shell morphology alone we conclude that this species may be best classified as P. (Eudolichotis) hauxwelli untill more material, hopefully allowing for anatomical and molecular studies, becomes available”.
I am very grateful to Graham Oliver for sending me the information and snapshots of this shell.