There are rarities, and then there are rarities. First, take the number of modern dance companies. Then remove all those who've been together for less than 35 years. Then subtract all but those devoted to African-American choreography. Among the very small handful left, the Denver-based Cleo Parker Robinson Dance Ensemble impressed regional audiences at the American Dance Festival in the 1990s. Mindful of black dance traditions but open to innovative new choreography, the group returns this week for a week-long community-based residency with master classes at Hayti Heritage Center and performances at Lyons Park and Durham School of the Arts, and a concert Friday and Saturday night at St. Joseph's Performance Hall. Tickets for the St. Joseph's performance are $18, $15 for students and seniors. For reservations or more info on the company's classes and public appearances, call 683-1709 ext. 22.