Abstract: | SYNOPSIS. Oocysts of Eimeria natricis sp. n. and Eimeria sipedon sp. n. were isolated from 2 Northern Water Snakes, Natrix sipedon sipedon (Linnaeus), in Iowa. Oocysts of E. natricis were elongate, slightly ovoid, averaging in size 32.3 × 17.5 μm; sporocysts averaged 15.7 × 8.2 μm. Oocysts of E. sipedon were broadly ovoid averaging in size 18.0 × 15.9 μm; sporocysts averaged 12.0 × 7.4 μm. In both species, sporocyst residua were present, but micropyles, polar granules and oocyst residua were lacking. |