Abstract. Herpetocypris brevicaudata Kaufmann, 1900 has only two previous records from the UK: from Marlborough, Wiltshire, (Lowndes, 1930) and from Garelochhead, Argyll and Bute (collected by A. J. Bruce in July 1958, and deposited in the NHM collections), two localities that correspond to those marked by Henderson (1990). A third locality, from near Sittingbourne, Kent, UK, is reported here.

Herpetocypris brevicaudata (Pl. 1; Fig. 1) and Heterocypris incongruens (Ramdohr, 1808) were found in a thick, brown algal layer at the bottom of a metal cattle trough, by the footpath leading from Rodmersham to Lynsted, near Dully Road, N51° 18′ 46.9′′ E000° 46′ 32.8′′. Samples taken on 6 December 2003 and 18 January 2004 produced abundant specimens of both ostracod species (i.e. tens of thousands). On 18 January 2004: temperature=3°C, pH=7.66, depth of sample 0.35 m, submerged macrophytes present. All specimens of H. brevicaudata were adult females, those of H. incongruens both adult females and juveniles.

Lowndes (1930) and Meisch (2000) suggested that H. brevicaudata is often mistaken for Herpetocypris reptans (Baird, 1835) and thus H. brevicaudata may be more common than records indicate. The wide calcified inner lamella (Pl. 1), the arrangement of the antenna natatory setae (Fig. 1) and the almost uniform green colouration of H. brevicaudata clearly separate it from H. reptans (Gonzalez Mozo et al., 1996).

Experimental data collected by Roca & Wansard (1997) on H. brevicaudata from Spain determined that at 12.4°C development is slower and survival rates lower than at higher temperatures. These experimental data, combined . . .