498 BIOLOGY OF THE PROTOZOA 



Sub-order 3. Hypostomina Schewiakoff 1890; em. Kahl. 



Family 1 . Nassulidae Blitschli. 



1. Opening of oral basket deep in a vestibule 



of which the external opening is nar- 

 rowed by a membrane Genus Nassula Ehr. 



Opening of oral basket on surface or in a 

 shallow, uncovered depression 2 



2. Basket opens in a deep depression with 



cilia or membrane on anterior edge; 

 small, oval, slightly flattened infusoria, 



with scattered trichocysts Genus Cyclogramma Perty 



Basket opens on surface ; usually distinctly 

 flattened forms, no trichocysts 3 



3. Basket opening, median; body margin with 



slight or no snout formation Genus Chilodontopsis Blochmann 



Basket strongly directed to right; right 

 margin of body shows a distinct snout- 

 like process in the mouth region. .Genus Orthodon Gruber 

 Family 2. Chlamydodontidae Clans 1874. 



1. The ciliated surface is separated from the 



unciliated surface by a narrow, hyaline, 



cross-striped ring Genus Chlamydodon Ehr. 



Cross-striped ring absent 2 



2. Ciliated ventral surface limited to a V- 



shaped median part and overlapped on 

 both sides by non-ciliated part. . .Genus Phascolodon Stein 

 Ciliated surface not thus limited 3 



3. Mouth a transverse slit in first quarter of 



body, with a clapper-like membrane 



Genus Gastronauta Engelm. 

 Mouth opening circular 4 



4. Gullet" with distinct basket; a cross row of 



bristles on the anterior flattened part 



Genus Chilodonella Strand 

 (= Chilodon Ehr.) 

 Basket indistinct; no cross row of bristles; 

 entire edge of body surrounded by dor- 

 sally directed spines Genus Cryptopharynz Kahl 



Family 3. Dysteriidae Clap, and Lach. 1S5S. 



1. Ventral side entirely ciliated; gullet with 



short stout rods Genus Hartmannula Poche 



( = Onychodactylus Entz) 

 Ventral surface with unciliated edge on at 

 least one side 2 



2. Powerful end spine is continuation of tail 



end ; ciliated area narrowed by unciliated 



edges on both sides Genus Scaphidiodon Stein 



Ventral ciliated area limited especially 

 from left 3 



3. Ciliated on ventral right side, and in post- 



oral area where rows shorten from right 



to left Genus Twchilioides Kahl 



Postoral cilia formed by extension of pre- 

 oral cilia to right of mouth and parallel 

 to right margin ; 1 or 2 adoral cross rows 

 may occur 4 



