Rhotacism in Latin is a well-known phonological generalisation which, in its paradigm cases, can be stated as a regular sound change of [s] to [r] between vowels. This change/rule is posited on the basis both of comparative evidence, e.g. *swesor Latin soror ‘sister’, and of paradigms in which final s alternates with medial intervocalic r, e.g. flos, floris ‘flower’. It is possible, however, to cite a number of exceptions to the basic r...