Scotty (SV) asked:
what's Latin for ''POS that doesn't belong on the ocean''?

Alan Gomes responded with finesse:
"Pars excrementi, quae non oportet esse in mari."

Horvath interjected in a scholarly way:
Close!

"Mare."


Alan Gomes, somewhat miffed, contradicted in this way:

Nope. The ablative for "sea" is "mari," not "mare."

--AG

So I looked it up.....

....from About.com:
Latin nouns of the third declension (such as mare)

here are the consonantal endings.

The endings of the Third declension masculine or feminine/neuter are
singular
nominative -/-
genitive -is/-is
dative -i/-i
accusative -em/-
ablative -e/-e

plural
nominative -es/-a
genitive -um/-um
dative -ibus/-ibus
accusative -es/-a
ablative -ibus/-ibus

Using rex, regis, m. (king), here is the paradigm:

singular
Nominative - rex
Genitive - regis
Dative - regi
Accusative - regem
Ablative - rege
Locative regi or rege
Vocative rex


The facts speak in favor of Horvath, it appears for the ablative.
Perhaps Gomes had in mind the locative?

Brian Whatcott Altus OK