THE CILIATES 



371 



T. excavatimi Hsiung, 1930 measures 

 95 to 135 by 55 to 90 jLt. It differs from 

 T. unifasciculatum in having a deep ellip- 

 tical excavation covered by a flap of cuti- 

 cle at its anterior end, and its cuticular 

 ridges are more prominent and the adja- 

 cent ones further apart. Hsiung (1930) 

 found this species in the colon of 1 out of 

 46 horses in Iowa. 



T. parvum Hsiung, 1930 measures 

 67 to 98 by 39 to 52 |Lt . It differs from the 

 other 2 species in lacking longitudinal 

 cuticular ridges. Hsiung (1930) found this 

 species in the colon of 1 out of 46 horses 

 in Iowa. 



Genus DITOXUM Gassovsky, 1919 



There is a large adoral zone of mem- 

 branelles near the anterior end and also 

 anterodorsal and posterodorsal zones of 

 membranelles. The macronucleus is 

 curved and club-shaped. 



Ditoxuni fiinimicleum Gassovsky, 1919 

 is elliptical with both ends rounded, 

 slightly flattened bilaterally, and measures 

 135 to 203 by 70 to 101 jm . It has a single 

 contractile vacuole. Hsiung (1930) found 

 this species in the colon of 2 out of 46 

 horses in Iowa. 



Genus TRIPALMAMA 

 Gassovsky, 1919 



There is an adoral zone of membran- 

 elles at the anterior end and also 2 dorsal 

 and 1 ventroposterior tuft-formed zones 

 of membranelles. The macronucleus is 

 shaped like an inverted U. A synonym of 

 this genus is Tricaudalla Buisson, 1923. 



Tripalmaria dogieli Gassovsky, 1919 

 measures 77 to 123 by 47 to 62|i. Beneath 

 the right side it has skeletal plates form- 

 ing a horseshoe with its open end directed 

 posteriad. Hsiung (1930) found this spe- 

 cies in the colon of 3 out of 46 horses in 

 Iowa. 



C. OTHER CILIATES 

 FAMILY BALANTIDIIDAE 



This holotrichasin, trichostomorid 

 family was once considered to belong in 

 the Heterotrichorida; Faure-Fremiet 

 (1955) showed its proper position. Cilia 

 are arranged in longitudinal rows over the 

 whole body. The peristome forms a pouch 

 with a triangular opening containing a 

 short adoral zone of membranelles. There 

 is no concretion vacuole. 



Genus BALANTIDIUM 

 Claparede and Lachmann, 1858 



Genus COCHLfATOXUM 

 Gassovsky, 1919 



There is an adoral zone of membran- 

 elles at the anterior end and also 1 anter- 

 odorsal, 1 posterodorsal and 1 postero- 

 ventral zone of membranelles. The 

 anterior end of the macronucleus is 

 curved. 



Cochliatoxum periachtum Gassovsky, 

 1919 is more or less cylindrical, with 

 both ends rounded, and measures 210 to 

 370 by 130 to 210fi. There is a contrac- 

 tile vacuole. Hsiung (1930) found this 

 species in the colon of 1 out of 46 horses 

 in Iowa. 



The body is ovoid, ellipsoid to sub- 

 cylindrical. The macronucleus is elon- 

 gated. There is a single micronucleus. 

 The contractile vacuole and cytopyge are 

 terminal. 



Many species of Balantidium have 

 been named, based on the host in which 

 they occur and on the size and shape of 

 their body and macronucleus (cf. Hegner, 

 1934; Kudo and Meglitsch, 1938). How- 

 ever, many of these are probably not 

 valid. For instance, McDonald (1922) 

 separated B. suis from B. coli, both from 

 swine, on the basis of its slenderer body 

 and straighter macronucleus, but Levine 

 (1940, 1940a) showed that Balantidium 

 from swine changed dimensions upon 



