Location: Unknown. Oocysts found in feces.
Geographic Distribution: North America.
Prevalence: Christensen (1938a) found this species in 10% of 100 sheep from Maryland and Wyoming.
Morphology: This species has been described by Christensen (1938a). The oocysts are ellipsoidal, 12 to 20 by 8 to 15 u with a mean of 14.2 by 10.0 u. Their length-width ratio is 1.2 to 1.7 with a mean of 1.43. A micropyle is imperceptible and there is no micropylar cap. The oocyst wall is thin, homogeneous, colorless to pale yellow to yellowish green, appears fragile and pallid, and is composed of 2 layers of which the outer is half as thick as the inner, with a single dark refraction line marking its inner edge. An oocyst polar granule and oocyst residuum are absent. The sporocysts are ovoid, without a sporocyst residuum. The sporozoites lie lengthwise, head to tail, in the sporocysts, and contain a spherical globule at each end. The sporulation time is 1 day.
Life Cycle: Unknown.
Remarks: In describing E. pallida, Christensen (1938a) said that it differed from E. parva is being narrower, pale, inconspicuous and colorless, and in having only a single black refraction line on the inner surface of the oocyst wall instead of 2 black refraction lines, one on each side of the inner wall. However, Kotlan, Pellerdy and Versenyi (1951) considered E. pallida a synonym of E. parva.