Description: LivingAmmoniaspecies and an inventory of dead assemblages from Adriatic subtidal, nearshoreenvironments were investigated at four stations off Bellaria, Italy.Ammonia falsobeccarii, Ammonia parkinso-niana, Ammonia tepida, andAmmonia venetawere recognized in the living (rose-bengal-stained) fauna, andAmmonia bellarian. sp. is described herein for the first time.Ammonia beccariiwas only found in the deadassemblage. The biometry of 368 living individuals was analysed by using light microscopic and scanning elec-tron microscopic images of three aspects. A total of 15 numerical and 8 qualitative parameters were measuredand assessed, 5 of which were recognized to be prone to a certain subjectivity of the observer. The accuracy ofnumerical data as revealed by the mean residuals of parallel measurements by different observers ranged from0.5 % to 5.5 %. The results indicated a high degree of intraspecific variability. The test sizes of the individualspecies were log-normally distributed and varied among the stations. Parameters not related to the growth ofthe individuals, i.e. flatness of the tests, dimensions of the second-youngest chamber, proloculus, umbilical andpore diameter, sinistral–dextral coiling, and umbilical boss size, were recognized as being species-distinctive incombination. They may well supplement qualitative criteria that were commonly used for species discriminationsuch as a lobate outline, a subacute or rounded peripheral margin, or the degree of ornamentation on the spiraland umbilical sides. The averages of the measured parameters were often lower than the range of previouslypublished values, mainly because the latter were retrieved from a few adult specimens and not from the wholeassemblage as in the present approach. We conclude that the unprecedented high proportions ofAmmonia bec-cariiin the northern Adriatic may well be artificial. A robust species identification without genetic analyses ispossible by considering designated biometric parameters. This approach is also applicable to earlier literaturedata, and their re-assessment is critical for a correct denomination of recent genotypes.