MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 505 



Key to Families 



5. On right edge of peristome are two simple 

 undulating membranes; a distinct pocket 



is absent Family 4. Lembidae 



Peristomial furrows with either a thick area 

 of cilia outside of which is an undulating 

 membrane, or a single thick undulating 

 membrane on the right edge; to right of 

 mouth and posteriorly a pocket with 

 small membrane is sunk below the ecto- 

 plasm Family 3. Philasteridae 



Family 1. Frontoniidae Kahl 1926. 



1. Except in Lembadion, no long caudal cilia; 



never a single caudal bristle 2 



With one or more caudal cilia, occasionally 

 fused in brush (Urocentrum) 22 



2. Mouth opening pointed anteriorly 3 



Mouth opening rounded or truncated ante- 

 riorly 10 



3. Mouth at most one-third body length. ... 4 

 Mouth one-half to four-fifths of body 



length 8 



4. Mouth truncated posteriorly; undulating 



membrane on left; partly fused mem- 

 brane-like cilia on right margin 5 



Mouth not truncated posteriorly; but 

 sharp-pointed or rounded 7 



5. Mouth without gullet-like, funnel-form 



posterior prolongation G 



Mouth with funnel-like gullet into which 

 membrane of left margin continues 



Genus Frontoniella Wetzel 

 G. Gullet fibrils strong and numerous; poste- 

 rior to mouth, a distinct line runs to 

 posterior end ; form not triangularly nar- 

 rowed posteriorly Genus Fronton in Ehr. 



Gullet fibrils delicate, sparse; ventral line 

 indefinite; narrows triangularly at pos- 

 terior region Genus Disemotostoma 



Lauterborn 



7. Mouth a small, sigmoid cleft; not at ante- 



rior pole; with 2 membranes Genus Sigmostomum Gulati 



Mouth elongate, from anterior pole; 2 mem- 

 branes; gullet with long fibrils. .Genus Leucoyhrydium Roux 



8. Mouth about one-half body length 9 



Mouth three-quarters to four-fifths body 



length (with long caudal cilia) . . . .Genus Lembadion Perty 



9. Anterior end pointed; body broadly oval 



Genus Leucophrys Ehr. 

 Anterior end rounded, body slender . Genus Turania Brodsky 

 10. Mouth oblique (anterior right to posterior 



left); ectoplasmic lip on right edge 11 



No ectoplasmic lip on right margin of 

 mouth 13 



