15 extent or degree of native fluency is unknown. There is some evidence that the Urus constituted a servant class (Hardman, personal communication). Differences among Aymara dialects have always been considered minor from colonial times to the present. The priests who went to the mines in Potosi to preach and hear confessions had no trouble understanding Aymara speakers from different provinces, according to the Jesuit missionary Ludovico Bertonio (1612, A 2). Bertonio (1603b and 1612) occasionally identified certain forms as preferred by the Lupaca but not until recent times have compilers of Aymara word-lists or grammars some- times indicated the geographical origins of the forms cited. The published literature gives no indication whatever of social differentiation of dialects as dis- tinguished from regional variation. 1-2.3 Summary description of La Paz Aymara The most complete and accurate ethnographic and grammatical description of Aymara to date, based on that spoken in Compi and Tiahuanaco, two communities near La Paz, Bolivia, is contained in Outline of Aymara phonological and grammatical structure by Hardman et al. (1975:3). The Outline describes Aymara as a polysynthetic language in which suffixes and retention or loss of vowels perform almost all grammatical functions.