PETER PERYER'S best-known photograph may be the dead cow with legs akimbo that featured on the poster and the cover of the catalogue for Second Nature, his 1995–97 traveling exhibition curated by Peter Weiermair and Gregory Burke. But there is a back story to Peryer's coolly composed images of the '80s and '90s. Before his topsy-turvy cow inflamed the sensibilities of New Zealand meat producers, Peryer was better known for his angst-ridden photographs of the '70s, including an ongoing series of portraits of his wife, Erika Parkinson. As a document of a marriage the series is concise, at least