Chapter 40 

 Order 2 Spirotricha Butschli (continued) 



Suborder 3 Ctenostomata Lauterborn 



THE ciliates placed in this group are carapaced and compressed 

 forms with a very sparse ciHation. The adoral zone is also re- 

 duced to about 8 membranellae: These organisms are exclusively 

 free living and sapropelic in fresh, brackish, or salt water. 



Posterior half of carapace with 4 ciliated rows on left and at least 2 rows 

 on right; with anterior row of cilia on left side. .Family 1 Epalcidae 

 Posterior half of carapace with cirrus-like groups on left only, none on 

 right; without frontal cilia 



Long ciliated band extends over both broad sides 



Family 2 Discomorphidae 



Short ciliated band ventral, extending equally on both broad sides. . . 

 Family 3 Mylestomidae (p. 666) 



Family 1 Epalcidae Wetzel 



Genus Epalxis Roux. Rounded triangular; anterior end pointed 

 toward ventral surface, posterior end irregularly truncate; dorsal 

 surface more convex; right carapace with 1 dorsal and 1 ventral 

 ciliary row in posterior region; usually 4 (2-3) median teeth; all anal 

 teeth without spine; with comb-like structures posterior to oral aper- 

 ture; 1-2 oval macronuclei dorsal; contractile vacuole posterior- 

 ventral; sapropelic in fresh or salt water. Many species. 



E. mirahilis R. (Fig. 313, a). 38-45m by 27-30^; fresh water. 



Genus Saprodinium Lauterborn. Similar to Epalxis; but some 

 (left and right) of anal teeth with spines; sapropelic in fresh or salt 

 water. Several species. 



S. dentatum L. (Fig. 313, 6). 60-80m long; fresh water. 



S. putrinium Lackey (Fig. 313, c). 50/x long, 40jli wide, about 15/z 

 thick; in Imhoff tanks. 



Genus Pelodinium Lauterborn. Right carapace with 2 median 

 rows of cilia, its median anal teeth fused into one so that there are 

 only three teeth. One species. 



P. reniforme L. (Fig. 313, d). 40-50)u long; sapropelic. 



Family 2 Discomorphidae Poche 



Genus Discomorpha Levander. Oval; ventrally directed anterior 

 spine long; posterior end without teeth or ridges; ciliated bands on 



665 



