Summary: The results are given of a biochemical study of 21 strains of C27. An Adansonian analysis was carried out by electronic computer on these strains and the Aeromonas strains studied in the previous paper (Eddy, 1962). The analysis confirms the proposal that the C27 strains should be excluded from the genus Aeromonas and a description of the new genus, Plesiomonas (Habs & Schubert, 1962), for these organisms is given. The analysis did not clearly establish Aer. formicans as a species distinct from Aer. punctata.