a claim in dependent form shall contain a reference to a claim previously set forth and then specify a further limitation of the subject matter claimed. Dedpendent claim 6, with intervening claims 1 and 2, recited
We recognize that the patentee was attempting to claim what might otherwisehave been patentable subject matter. Indeed, claim 6 could have been properlydrafted either as dependent from claim 1 or as an independent claim—i.e., "thehemicalcium salt of atorvastatin acid." But, we "should not rewrite claims topreserve validity." Nazomi Commc'ns, Inc. v. Arm Holdings, PLC, 403 F.3d 1364,1368 (Fed. Cir. 2005); see also Rhine v. Casio, Inc., 183 F.3d 1342, 1345 (Fed.Cir. 1999) ("[I]f the only claim construction that is consistent with theclaim's language and the written description renders the claim invalid, then . .. the claim is simply invalid.").