This class corresponds to the nouns of the Latin third declension that had the genitive plural ending -ium (rather than -um). In Latin, the consonant stems gradually merged with this class. This process continued into the historical era; e.g. in Caesar's time (c. 50 BC) the i-stems still had a distinct accusative plural ending -īs, but this was replaced with the consonant-stem ending -ēs by the time of Augustus (c. AD 1). In Proto-Italic, as in the other Italic languages, i-stems were still very much a distinct type and showed no clear signs of merging.
