Abstract.Li/Ca ratios in modern brachiopod shells generally correlate inversely with growth temperature, ranging from -20 pmol/mol at 30°C to -50 ~moljmol at ooc with no apparent interspecific have Li/Ca ratios around 70% of the modern average. These Li/Ca ratios can be explained by either somewhat higher temperature with constant seawater Li/Ca, somewhat lower seawater Li/Ca at constant temperature, or a combination of slightly elevated temperature and slightly lower seawater Li/Ca.