Hmmm.Maltedo is not a surname I have seen before, but that doesn't mean anything. I have heard of Lagomarsino families in Boston, tho none of "mine". Do you have them in the 1900 census?
Typically, marriages took place in the parish of the bride.After that, the couple generally lived in the town/parish of the groom.If their children were born in Italy, and your Lagomarsino was from S. Maria in Certenoli, their births/baptisms would be recorded there.It's worth a shot.
Have you seen these web sites?They're among my favorites.
www.parrocchie.it gives addresses for parishes in Italy. Where it says "citta" (city), enter San Colombano Certenoli and you will get a list of all parishes in that comune including S. Maria Assunta in Certenoli whose address is: Parrocchia S. Maria Assunta in Certenoli Piazza della Chiesa, 1, Certenoli, 16040, S. Colombano Certenoli, (GE)
www.labo.netgive it a "cognome" (surname) and see where in Italy it appears. Useful in guessing where a family might have originated.
Good luck, and let me know if you find the 1st name for your Lagomarsino.