508 BIOLOGY OF THE PROTOZOA 



Family 4. Lembidae Kahl 1931. 



Only one genus— Lembus Cohn (Fig. 204) 

 Family 5. Pleuronematidae Kent 1882. 



1. Small, test-building, fresh water species 



Genus Calyptotricha Phillips 

 Not test-building 2 



2. Marine; ectocommensal on Hydractinia 



Genus Pleurocoptes Wallengren 

 Not ectocommensal 3 



3. Undulating membrane without distinct 



pocket; peristome oblique from anterior 



right to posterior left Genus Ctedoctema Stokes 



Undulating membrane pocket distinct; 

 hardly ever oblique 4 



4. Body fiat; peristome continues as groove 



posterior to mouth Genus Cristigera Roux 



Peristome on right side, without groove 

 posterior to mouth 5 



5. Large (70 to 180), striking forms (i 



Small (up to 50); no semicircular swelling 



of peristome Genus < 'yclidium ( >. F. Muller 



0. Posterior sensory bristles; 1 contractile 



vacuole; peristome begins at anterior 

 end; semicircular swelling to left at 



mouth region Genus Pleuronema Dujardin 



Sensory bristles distributed over body, 2 

 to 3 times longer than cilia; peristome 

 begins on first quarter, without oral 

 swelling^ C. V. numerous Genus Histiobalantium Stokes 



Sub-class II. SPIROTRICHA Butschli 1889; km. Kahl 1931. 



Key to Orders 



1. Only free cilia present; exceptionally tufts 



of cirrus-like aggregates 2 



Ciliation exclusively cirri; dorsal rows of 

 short, delicate, slightly movable bristles 



Order 4. Hypotrichida 



2. Body uniformly ciliated; in flat forms no 



cilia dorsally; in ectoparasitic Lichno- 

 phoridae cilia around edge only of at- 

 taching disc; frontal field ciliated 



Order 1. Heterotrichida 

 Cilia much reduced or absent 3 



3. Small, flattened, cara paced forms whose 



peristome has only 8 membranelles 

 which lie in a ventral hollow. . .Order 3. Ctenostomida 

 Transverse section circular; cilia much 

 reduced; adoral zone encloses a non-cili- 

 ated frontal field Order 2. Oligotrichia 



Order 1. Heterotrichida Stein. 



Key to Finn i lies 



1 . Ciliation complete, with uniform cilia .... 2 

 Ciliation absent or limited to ventral side . . !) 



