410 BIOLOGY OF THE PROTOZOA 



Family 1. Peritromidse, Stein. 



One genus with the characters of the family- 

 Genus Peritromus 

 Family 2. Urostylidse. 



1. Ectoparasitic on Hydra, etc Genus Kerona 



Free-living forms, usually bottom feeders . . 2 



2. No differentiated frontal cirri 6 



With from three to several frontal cirri .... 6 



3. Ventral rows of cilia straight 4 



Ventral cilia rows spiral 5 



4. With neck and tail; six to nine rows of cilia 



(Fig. 174) Genus Epiclintes 



No neck or tail; two marginal; two ventral 



rows cilia Genus Holosticha 



5. Peristome long; often tube-dwelling (Fig. 



173, p. 390) Genus Stichotricha 



Peristome only half the length of proboscis. 



Genus Sparotricha 



6. Ventral surface covered with fine cilia 



Genus Trichogaster 

 Ventral surface with few rows of cilia 7 



7. No anal cirri; two to four rows of ventral 



cilia 8 



With anal cirri 9 



8. No long caudal cilia or bristles (Fig. 1, 



frontispiece) Genus Uroleptus 



With three caudal cilia or bristles . . Genus Strongylidium 



9. Two rows marginal; two to three rows ven- 



tral cilia (Fig. 175) Genus Amphisia 



Two rows marginal; five to seven rows ven- 

 tral ciha Genus Uroslyla 



Family 3. Pleiirotrichidse, Biitschli. 



1. Posterior end drawn out as a distinct tail 



Genus Urosoma 

 Posterior end not tail-like 2 



2. Peristome very narrow 3 



Peristome broad, triangular 4 



3. Five anterior ray-like spikes (membran- 



elles) Genus Actinotricha 



No ray-like spikes ; three caudal cirri Genus Gonostomum 



4. Body very flexible; tail bristles short, if any 5 

 Body slightly flexible or rigid 6 



5. Five to six frontal; irregular rows of ventral 



cirri Genus Gastrostyla 



Eight frontal, five ventral, undeveloped 



caudal cirri (Fig. 175) Genus Oxytricha 



6. No caudals; marginal row of cilia unbroken 



posteriorly 7 



Three caudals; marginal row broken pos- 

 teriorly Genus Stylonychia 



7. Row of anal cirri broken; two nearer pos- 



terior end (Fig. 176) Genus Pleurotricha 



Anal cirri form a continuous line 8 



8. Large; anterior and posterior ends truncate 



(Fig. 172, p.) 389 Genus Onychodromus 



Small; oval to ellipsoidal (Fig. 175). Genus Histrio 



