MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 517 



Key to Families 

 2. Cirri essentially typical; ventrals may be 

 reduced; marginal rows present; dorsal 



bristles present Family 1. Oxytrichidae 



Marginal and ventral rows absent 



Family 2. Euplotidae 

 Key to Genera 

 Family 1. Oxytrichidae Ehr. 1838. 



1. Transverse cirri absent (not always easily 



seen) 2 



Transverse cirri present (not always easily 

 seen) 10 



2. Ventral and marginal rows not distinctly 



spiral 3 



Ventral and marginal rows distinctly 

 spiral, overlapping dorsum 7 



3. Long, band form, posterior pointed or 



rounded (salt lakes) with only 2 feath- 

 ered frontal membranelles Genus Cladotricha Gajevskaja 



Other types 4 



4. Frontal cirri not limited to 3 to 6 but are 



numerous, distributed in rows not dis- 

 tinct from ventral cirri 5 



Frontal cirri reduced to 3; no other cirri. . 6 



5. Small, oval (50 to 100/x) ; with long, widely 



separated bristle-like cirri Genus Psiloiricha Stein 



Frontal cirri arranged cross-wise over 

 frontal field Genus Eschaneustyla Stokes 



6. Elongate, narrowed to tail-like end; usu- 



ally 2 ventral rows Genus Uroleptus Engelm. 



Ovoidal forms with 5 to 8 rows of long 

 ventral cirri not different from marginal 

 rows Genus Kahlia Horvath 



7. Fresh water forms with broad peristome; 



posterior end short spine-like. . . .Genus Hypotrichidium Ilowaisky 

 Slender forms with narrow peristome 8 



8. Peristome only slightly narrowed; adoral 



zone short Genus Strongylidium Sterki 



Peristome neck-like, narrowed ; adoral zone 

 on left side 9 



9. Peristome region little or not at all exten- 



sible Genus Stichotricha Perty 



Peristome region highly distensible. .Genus Chaetospira Lachmann 



10. No specialized frontal cirri; ventral rows 



run to anterior end without cirri special- 

 ization 11 



Frontal cirri strongly developed; first 3 

 especially 16 



11. Small, oval, marine forms with very large 



peristome 12 



Otherwise formed, or not marine 13 



12. Transverse cirri small; not continued to 



posterior end Genus Caryotricha Kahl 



Transverse cirri long and stiff, reaching 



well beyond posterior end Genus Stylocoma < '.ruber 



