In statistics, a point that separates out (a multiple of) 25% of the data set is called a "quartile". Similarly, if it separates out 20% of the data, it's a "quintile", 1% a "percentile", and in general a "quantile".
The first of these seems to come transparently from quartus + -ilis, and the "-ile" ending in English usually comes through French. However, I've never seen such a formation in Latin.
I would normally have attributed this to a later development—except that in the early calendar, the fifth and sixth months were called quintilis and sextilis. This makes me wonder whether there were other adjectives like *quartilis, which were just obscure and/or regularly-formed enough not to appear in L&S.
So: Are adjectives from ordinal + -ilis attested? If so, what did they mean?