This group comprises:
Undella claparedei (Entz Sr., 1885)
Undella globosa (Brandt 1906-1907)
Undella perpusilla (Kofoid and Campbell, 1929)
Undella subacuta Cleve, 1901
Undella subcaudata subcaudata (Jörgensen, 1924)
Diagnosis: Because of continuous morphologic transitions between U. claparedei (Entz Sr., 1885), U. subcaudata subcaudata (Jörgensen, 1924), U. globosa (Brandt 1906-1907), U. perpusilla (Kofoid and Campbell, 1929), and U. subacuta Cleve, 1901, these species are placed in the U. claparedei group. Slightly different forms within this spectrum of variability are tentatively attributed to dissimilar environmental settings.