Latina Christiana II - Quiz XXI error?

[a_two_z@earthlink.net]

I wondered if someone could tell me whether there is an error in the declension of the noun "mare" in the answer key for Quiz XXI? This is a third declension i-stem noun and I don't understand why it is declined like this:
mare, maris, mari, mare, mari, maria, marium, maribus, maria, maribus when the endings for the third declension i-stem nouns are --, is, i,--, e, a, ium, ibus, a, ibus. The errors I noted would be for the singular ablative (note the i instead of the e ending) the nominative plural (note the ia instead of the a) and the accusative plural (same as nominative plural) which are not following the usual endings. Am I missing something here? Calgon, take me away~~~~~~~~~~~~

[DebbieCantrell]

I asked my Latin teacher/friend and she agreed that there is an error in the quiz answers. It should read: mare, maris, mari, mare, mare, mara, marium, maribus, mara, maribus.

[pobrien]

Mare is a neuter i-stem noun of the 3rd declension. The correct declension is as follows:
mare, maris, mari, mare, mari
maria, marium, maribus, maria, maribus
The confusion is our fault, really, because the i-stem declensions are not covered in the book (there is a note about mare in Lesson 21 of the teacher book, but it does not give the whole declension.) But, to make a long story short, there are many i-stem nouns in the 3rd declension. These do not decline like ordinary 3rd declension nouns, and they are called 'i-stem' because the stem does end in -i, which appears in most of the forms. There are different i-stem declensions for masculine-feminine nouns and neuter nouns. Mare is the only i-stem neuter 3rd declension noun in Latina Christiana, but if you want to see how the whole 3rd declension works, i-stems included, check out a more advanced Latin grammar (Henle, for example) or any of the good online sites. Paul OBrien.