Type host: Spermophilus spilosoma.

Type locality: Central America: Mexico, 7 mi. N of Rincon de Romos, Aguascalientes.

Other localities: Central America: Mexico, Chihuahua.

Description of oocyst: Oocyst shape: subspheroid; wall thickness: 1; layers: 1; outer layer colour: colourless to pale yellow; outer layer texture: smooth; micropyle: absent; OR: sometimes present; OR characteristics: absent or composed of a few homogenous bodies; OR L x W: not given; PG: present; number of PGs: 1-2; PG shape: not given; PG L x W: not given; size: 17.7 x 16.1 (15-20 x 13-18); L/W ratio: 1.1 (1.0-1.2). Distinctive features of oocyst: none.

Description of sporocysts and sporozoites: Sporocyst shape: elongate ovoid; size: 11.5 x 6.0; SB: absent or inconspicuous; SB characteristics: not given; SSB: absent; PSB: absent; SR: present; SR characteristics: a large amount of finely granular material; SR size: not given; SP: lay either at the end of the sporocysts or somewhat longitudinally. Distinctive features of sporocyst: none.

Remarks: This species has been observed only in S. spilosoma (Levine et al., 1958; Ivens et al., 1959).

References: Levine et al. (1958); Ivens et al. (1959).