MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 521 



Family 1. Oxytrichidae Ehr. 1838. 



28. Posterior end tail-like or pointed. . .Genus Urosoma Kowalewsky 

 Posterior end not tail-like or pointed 29 



29. Right peristome edge hook-like and turned 



to left, spirally rolled anteriorly. .Genus Steinia Diesing 

 Peristome edge does not reach to adoral 

 zone 30 



30. Body soft, plastic, occasionally contractile. 31 

 Body stiff 33 



3 1 . Marginal rows continuous posteriorly 



Genus Oxytricha Bon- 

 Marginal rows broken posteriorly 32 



32. No caudal cirri Genus Tacky soma Stokes 



With caudal cirri Genus Opisthotricha Kent 



33. Marginal rows continuous posteriorly; no 



caudal cirri Genus Histn'o Sterki 



Marginal rows broken posteriorly; with 

 stiff caudal cirri Genus Stylonychia Ehrenberg 



Family 2. Euplotidae Ehr. 1838. 

 Key to Genera 



1 . Anterior third of body head-like because of 



two lateral notches Genus Discocephalits Ehr. 



Anterior third not head-like 2 



2. No special steering cirri near posterior end . 3 

 Near posterior end 1 or 2 groups of power- 

 ful cirri 5 



3. Left marginal cirri row continuous; 4 mac- 



ronuclei, ellipsoid marine form. . .Genus Certesia Fabre-Dom. 

 Left marginal cirri absent, or isolated 

 single ones 4 



4. Frontal part of adoral zone lies in flat 



furrow Genus Euplotes Ehr. 



Frontal part of adoral zone separated from 

 dorsum by deep funnel-like depression 



Genus Crateromorpha 



Perejaslawzewa 



5. One group of 3 powerful cirri, on right 



dorsal Genus Diophrys Dujardin 



Powerful cirri in addition to 3 on right side, 



dorsal Genus Uronychia Stein 



Family 3. Aspidiscidae Stein 1859. 

 Only one genus — Aspidiscus Ehr. 



Sub-class III. PERITRICHA Stein. 



1. No peristomial trench; attaching disc 



ciliated Family Urceolariidae 



2. With peristomial trench; posterior cilia 



temporary Family Vorticellidae 



Family 1. Urceolariidae Stein. 



1 . Forms with smooth attaching ring . . Genus Urceolaria Stein 

 Forms with toothed ring 2 



2. With special tactile cilia Genus Trichodina Ehr. 



Without special tactile cilia Genus Acyclochaeta Zick 



