Abstract:  This study points out some basic problems of linguloid systematics and proposes solutions for them. A taxonomic examination of the unique species of the genus Obolus found in the Upper Cambrian of Estonia and Russia, O. apollinis (= O. ruchini, O. transversus, O. rebrovi and Ungula convexa) is used as an example of a methodology employing all of the characters valid for distinguishing species of both extant and fossil Lingulidae. These characters are: - umbonal region; - body musculature; - septa or ridges; - main mantle canals - as established and figured by EMIG (1982, 1983) and BIERNAT and EMIG (1993). All of them have been determined to be taxonomically stable and have been studied and compared to take into account intraspecific variability; they should be used to describe or to redescribe any taxon of the superfamily Linguloidea. Characters of the shell and valves, such as shape, size, and dimensional ratios have no taxonomic value.

 Abstract:  Diatom assemblages and water chemistry were studied in 13 shallow salt lakes in the southern part of the Bolivian Altiplano. At each locality bottom sediment and water samples were collected simultaneously. Relationships between the composition of the diatom assemblages and variations in water chemistry were collated in order to permit the estimation of ancient water chemistries based on changes in the make up of fossil diatom associations in older sediments. Weighted Averages treated by Partial Least Squares regression (WA and WA-PLS methods) allowed an estimation of optima and the relative tolerances of 61 species to variations in salinity and to the relative quantities of the 15 chemical elements studied, among them boron and lithium.