Type host: Cynomyc ludovicianus (Andrews, 1928).

Synonyms: Eimeria bilamellata; E. eubeckeri.

Other hosts: Cynomys gunnisoni; C. leucurus; C. ludovicianus; Cynomys sp.; Spermophilus armatus; S. beecheyi; S. citellus; S. columbianus; S. elegans; S. franklinii; S. lateralis; S. richardsonii; S. townsendii; S. tridecemlineatus; S. variegatus.

Type locality: Andrews' (1928) host animal (Cynomys sp.) was from an "animal supply house." He did the analysis in North America: USA, Ohio, but it is not clear where the hosts originated.

Other localities: Europe: Czech Republic; North America: Canada, Alberta; USA, California, Colorado, Idaho, Iowa, Ohio, Utah, Wyoming.

Description of oocyst: Oocyst shape: ovoid; wall thickness: 1.5-2.5; layers: 2; outer layer proportion of total thickness: not given; outer layer colour: brownish-yellowish, transparent; outer layer texture: rough; inner wall characteristics: orange-yellow; micropyle: present; micropyle width: 5-6; MC: absent; OR: absent; PG: 0-1; oocyst L x W: 35.4 x 30.0 (33-37 x 28-32); L/W ratio: 1.2. Distinctive features of oocyst: the largest eimerian species with a MP described from the Marmotini.

Description of sporocysts and sporozoites: Sporocyst shape: ovoid; size:13-17 x 8-12; SB: present; SB L x W: not given; SB characteristics: small (in drawing); SSB: absent; PSB: absent; SR: present; SR characteristics: coarsely granular, large amounts; SR size: not given; SP: attenuated reniform, 12-16 x 4-7; no interior structures observed. Distinctive features of sporocyst: the SR is membrane-bound (in drawing), but this feature was not mentioned by Andrews (1928).

Material deposited: USNPC No. 87250 (phototype).

Remarks: Eimeria cynomysis was described in "the North American prairie dog," Cynomys sp., likely C. ludovicianus (Andrews, 1928). Later, Hall & Knipling (1935) found a species in S. franklinii that they called E. eubeckeri (27.6-40.2 x 21.0-32.4), but Levine & Ivens (1965) synonymised it with E. bilamellata (25.6-35.6 x 22.4-25.6) (which we synonymize with E. cynomysis), and we agree. Vetterling (1964) emended the original description of E. cynomysis, but his oocysts were smooth-walled and had a prominent SB while those of E. cynomysis described by Andrews (1928) were rough-walled with an inconspicuous SB. We rename Vetterling's species in this paper (below) and synonymize E. bilamellata with E. cynomysis because the oocysts of both forms are indistinguishable from each other. Wilber et al. (1994) noted that oocysts sometimes contain 1 PG, whereas Andrews (1928) found no PG and Henry (1932) does not mention a PG.

References: Andrews (1928); Hall & Knipling (1935); Henry (1932); Hilton & Mahrt (1971); Kietzmann and Kietzmann, 1987; Pellérdy & Babos (1953); Ryšavy (1957); Seville (1997); Seville & Stanton (1993b); Seville & Williams (1989); Seville et al. (1992); Shults et al. (1990); Stanton et al. (1992): Thomas & Stanton (1994); Todd et al. (1968); Torbett et al. (1982); Vetterling (1964); Wilber et al. (1994).