Amicae curiae, rarae aves (& molon labe?)
A conversation with some students about the proper captions for briefs led me to a search for briefs amicae curiae, which in turn led me to a Brief of Amicae Curiae 126 Women State Legislators and Academics in Support of Respondent in D.C. v. Heller. ("What all Amicae share, however, is their devotion to the ability of women to legally and effectively defend themselves in situations that pose serious and immediate bodily injury.") A rare example indeed, though there are several others (as well as several that seem to just be mislabeled, perhaps based on a misunderstanding of what "amicae" means). The brief was filed by M. Carol Bambery, Sarah Gervase and Sue Wimmershoff-Caplan, though note that it is the sex of the client-signatories, not the sex of the lawyers, that is relevant.
Sure, it could have perfectly properly been a brief amici curiae, just as briefs of neuter entities (e.g., colleges) are amicus curiae briefs rather than amicum curiae briefs, and "brief of amici curiae" doesn't get turned into the genitive "amicorum curiae"—law Latin isn't Latin Latin (thank Jupiter). Still, a pleasant bit of linguistic fussiness; I found only a handful of other amicae curiae briefs in my Westlaw search.
Thanks to my brother Sasha for Latin consulting; all remaining errors are the fault of residents of Soli.