Those perennials keep putting forth their homely little blooms. Ian Anderson has been the cartoon-voiced, flute-playing leader of Jethro Tull for 24 years. Even more amazing is the fact that through fat times (the group sold about a zillion records in the early '70s) and thin (most of the years since) Jethro Tull has never put out an album anyone but die-hard fans of the band's faux-Elizabethan art-rock would find listenable. It's a tradition the band is hardly in a position to break at this late date. Classic-radio fodder ''This Is Not Love'' and ''Doctor to My Disease'' leads off each side of Catfish Rising. The rest is tuneless self-indulgence. C-

