370 



THE CILIA TES 



44 to 80/1. It has 4 or 5 contractile vac- 

 uoles. Its posterior end forms a tail re- 

 sembling that of a fish. Hsiung (1930) 

 did not find this species in Iowa horses. 



C. scutigerum Strelkov, 1928 differs 

 from C. bipalmatuni in having a shield- 

 like skeletal plate interrupted by 2 longi- 

 tudinal grooves on the left side instead of 

 a simple, narrow plate. It measures 132 

 to 210 by 63 to 90pt and has 5 or 6 con- 

 tractile vacuoles. Hsiung (1930) found 

 this species in the cecum of 24 and the 

 colon of 4 out of 46 horses in Iowa. 



C. affinae Strelkov, 1928 differs from 

 C. bipalmatuni in having a heavy skeletal 

 plate and in that the micronucleus is near 

 the anterior end of the macronucleus. It 

 measures 92 to 141 by 45 to 58 ji. Hsiung 

 (1930) found this species in the cecum of 

 3 and the colon of 1 out of 46 horses in 

 Iowa. 



C. corrugatum Hsiung, 1930 meas- 

 ures 135 to 195 by 70 to 112(x. It has a 

 ventral dentiform projection, and its cu- 

 ticle is corrugated. The anterior end of 

 its macronucleus is not hooked. The 

 linear skeletal plate is quite indistinct. 

 There are 4 or 5 contractile vacuoles. 

 Hsiung (1930) found this species in the 

 cecum of 7 and the colon of 1 out of 46 

 horses in Iowa. 



Genus SPIRODINIUM Fiorentini, 1890 



The body is elongate and more or 

 less fusiform, with an adoral zone of mem- 

 branelles at the anterior end. An anterior 

 ciliary zone encircles the body at least 

 once, and a posterior ciliary arch spirals 

 half-way around the body. There is a 

 dorsal cavity of unknown function lined 

 with stiff rods. 



Spirodinium equi Fiorentini, 1890 

 measures 77 to 180 by 30 to 74 p.. Its 

 macronucleus is elongated, with rounded 

 ends. There is a large contractile vac- 

 uole just back of the anterior membran- 

 elles. Hsiung (1930) found this species in 

 the colon of 3 out of 46 horses in Iowa. 



Genus TftlADINIUM Fiorentini, 1890 



The body is more or less helmet- 

 shaped and compressed, with an adoral 

 zone of membranelles at the anterior end. 

 There are ventral and dorsal posterior 

 zones of membranelles. There may or 

 may not be a caudal projection. 



Triadinium caudalum Fiorentini, 1890 

 measures 50 to 105 by 36 to 85 ;j and has 

 a long, slender tail. The macronucleus 

 is bent like a question-mark. There is a 

 single contractile vacuole. Hsiung (1930) 

 found this species in the colon of 3 out of 

 46 horses in Iowa. 



T. galea Gassovsky , 1919 measures 

 58 to 88 by 50 to 70 fi and lacks a tail. It 

 has a long macronucleus running longi- 

 tudinally along the left surface, and 2 con- 

 tractile vacuoles. Hsiung (1930) found 

 this species in the colon of 3 out of 46 

 horses in Iowa. 



T. mmimum Gassovsky, 1919 meas- 

 ures 32 to 50 by 31 to 42 ji and has a slen- 

 der tail. The macronucleus is ellipsoidal. 

 There is a single contractile vacuole. 

 Hsiung (1930) found this species in the 

 colon of 2 out of 46 horses in Iowa. 



Genus TETRATOXUM 

 Gassovsky, 1919 



The body is slightly compressed and 

 has 2 anterior and 2 posterior zones of 

 membranelles. 



Tetratoxum unifasciculatum (Fioren- 

 tini, 1890) Gassovsky, 1919 measures 104 

 to 168 by 62 to 100 fi . It is irregularly 

 elliptical, with both ends rounded, and has 

 7 to 9 longitudinal, cuticular ridges on 

 both the dorsal and ventral surfaces of the 

 body. Lateral cuticular extensions at the 

 posterior end form 2 caudal sheaths. The 

 macronucleus is elongate, with a short 

 hook at the anterior end. There is a large 

 contractile vacuole under its curvature. 

 Hsiung (1930) found this species in the 

 colon of 2 out of 46 horses in Iowa. 



