Language Log has an interesting post concerning the formation of scientific nomenclatures which are named in honor of those who discovered them. Sally Thomason wonders why female scientists receive attribution with only the feminine genitive suffix -ae but males with -i or -ii.
The gist: non-Latin names of these biologists has been notoriously problematic, and different methods of Latinization have led to two different surface forms of the masculine genitive suffix. So while evidence of it is slim, there is no reason why femine suffixes in -iae and -ia should not be present.
However, contributions by Ben Fortson and Don Cameron are always worth reading.
So the reason all this is relevant is that let's say you want to Latinize a non-Latin family name. A non-Latin family name kind of corresponds to the gentilicium but also kind of corresponds to the cognomen; there's no exact equivalent either way. So one could defensibly tack on either -ius or -us to the non-Latin name to do the trick. Falling into the former camp are Latinized names like Gronovius (originally Gronov), Lipsius (-us or -ius and usually the correct one was used. This can extend to German names of ultimately Latin origin, e.g. Camerarius being the rendering of Camerer (chamberlain).Mutatis mutandis the same issues obtain with women's last names. The names of Roman women were just feminizations of male names (Julia Greyia instead of Greya (to form the genitive greyae in Bathylagus greyae).
The International Code of Zoological Nomenclature (4th edition, Sec. 31.1.2) specifies one -i, but under 31.1.3, about preservation of the original spelling, both cuveri and cuverii are admissible. The trouble comes from different conventions of Latinizing modern proper names. Originally in Latin names like Marcus have genitive Marci and names like Livius have genitive Livii. So do you want to Latinize my name as Cameronus or Cameronius? You have a choice. Then the genitives would be Cameroni or Cameronii. Modern custom following the Code is to use one -i.Check out the rest of the post here.