516 BIOLOGY OF THE PROTOZOA 



Family 5. Cycloposthiidae Poche 1913. 



7. Forms with adoral zone and 2 long rows of 



membranelles in spirals Genus Spirodinium Fiorentini 



Forms with adoral zone and short dorsal 

 rows, 1 caudal and 1 occipital Genus Ditoxum Gassowsky 



8. Adoral zone very reduced ; 2 rows of mem- 



branelles anterior and 2 rows posterior 



Genus Tetratoxum Gassowsky 

 Adoral zone prominent 9 



9. Adoral zone and 3 rows of membranelles, 



1 occipital and 2 caudal Genus Cochliatoxum Gassowsky 



Adoral zone and row of membranelles mak- 

 ing at least 3 spirals about the body; the 

 row is broken at regular points by skel- 

 etal lappets Genus Troglodytella 



Brumpt and Jouex 



Order 3. CTENOSTOMIDA (Lauterborn) Kahl 1931. 

 Key to Families 



1. Posterior carapace has 4 rows of cilia on 



left, 2 on right— also 1 row of cilia on left 



frontal edge Family Epalcidae 



No frontal cilia; posterior row absent on 

 right side; on left side cilia are fused to 

 long cirrus-like groups 2 



2. Broad, long, ciliated band extends over 



both broad sides Family Discomorphidae 



Ciliated band is short; extends equally on 



both sides Family Milestomidae 



Key to Genera 



Family 1. Epalcidae Wetzel 1928. 



1. Only 1 dorsal and 1 ventral row of cilia; 



number of median teeth usually 4, often 



indefinite 2 



Right carapace with 2 median rows of cilia ; 

 its median teeth fused to one; 3 teeth in 

 all Genus Pelodinium Lauterborn 



2. At least some anal teeth (left and right) 



with spines Genus Saprodinium Lauterborn 



Anal teeth all without spines Genus Epalxis Roux 



Family 2. Mylestomidae Kahl 1931. 



1. Right hind end with 2, left with 1 great 



notch Genus Atopodinium Kahl 



Notches absent, or very small one on right 



Genus Mylestoma Kahl 

 Family 3. Discomorphidae Poche 1913. 

 Only one genus — Discomorpha Levander 



Order 4. HYPOTRICHIDA Stein s. str. 

 Key tn Families 



1. Adoral zone complete; dorsal bristles pres- 

 ent 2 



Adoral zone reduced to small, encapsulated 

 pre-oral part; on anterior left is an incon- 

 spicuous remnant of membranelles which 

 are very small and cirrus-like. .Family 3. Aspidiscidae 



