408 BIOLOGY OF THE PROTOZOA 



3. Pear-shape; base widest; with pigment spot 



Genus Fabrea 

 Compressed ; frontal field oblique (Fig. 56, 



p. 107) Genus Climacostomum 



Family 2. Bursaridae, Stein. 



1. Free-living 2 



Parasitic; peristome to center of body 



Genus Balantidium 



2. Frontal field deeply insunk ; sac-like 3 



Body worm-like, very contractile (Fig. 171) 



Genus Condylostoma 



3. Walls of sac with cortical trichocysts Genus Thylakidium 

 Walls of sac without trichocysts (Fig. 84, 



p. 160) Genus Bursaria 



Family 3. Plagiotomidae, Clap, and Lach. 



1. Free-living 2 



Internal parasites 6 



2. Laterally compressed 3 



Not compressed 4 



3. Peristome oblique with spiral gullet Genus Helicostoma 

 Peristome oblique, straight; usually pink 



(Fig. 174) Genus Blepharisma 



Adoral zone spirallj- wound from end to end 



Genus Phacodinium 



4. Body long, narrow; peristome narrow, 



straight (Fig. 30, p. 70) Genus Spirostonium 



Body ellipsoidal, not contractile 5 



5. Body straight , two crescentic oral lips 



Genus Porpostoma 

 Body twisted anteriorly; no crescentic lips 



(Fig. 171) Genus Metopus 



6. Form oval to bean-shape (Fig. 171) Genus Nyctotherus 

 Elongate; pointed anteriorly; truncate 



below Genus Plagiotoma 



Family 4. Gyrocorycidse, Stein. 



Anterior end rounded; umbrella-like (Fig. 174) 



Genus Coenomorpha 

 Anterior end flattened ; two bands of cilia 



Genus Trochella 

 Family 5. Ctenostomidae, Lauterborn. 



1. Anterior end with ventrally pointed spine 2 



Without ventrally directed anterior spine 3 



2. With two unequal spines on the right side 



Genus Discomorpha 

 Seven or eight posterior spines; none on 



sides Genus Saprodinium 



3. Posterior end with bisected incut. . .Genus Pelodinium 

 Posterior drawii out into seven to eight 



blunt i)rocesses Genus Epalxis 



Order III. OLIGOTRICHIDA, Butschli. 



1. Parasitic in stomach Family 3. OphryoscolecidjE 



Free-living 2 



2. Without house or test Family 1. H.\lteriid.e 



With house or test (mainly marine) . Family 2. TiNTiNNiDiE 



