SPIROTRICHA, OLIGOTRICHA 657 



Genus Eremoplastron Kofoid and MacLennan. Adoral and dorsal 

 zones at anterior end; a single narrow skeletal plate beneath right 

 surface; triangular or rod-like macronucleus, anterior end of which 

 is often bent ventrally; 2 contractile vacuoles; in cattle, antelope, 

 sheep, reindeer. Numerous species. 



E. hovis (Dogiel) (Fig. 309, c). 52-100m by 34-50^; in cattle and 

 sheep. 



Genus Eudiplodinium Dogiel. Adoral and dorsal zones at anterior 

 end; a single, narrow, skeletal plate beneath right surface; rod-like 

 macronucleus with its anterior end enlarged to form a hook opening 

 dorsally; pellicle and ectoplasm thick; 2 contractile vacuoles with 

 heavy membranes and prominent pores; in cattle. 



E. maggii (Fiorentini) (Fig. 309, d). 104-255ai by 63-170m; in cat- 

 tle, sheep and reindeer. 



Genus Diploplastron Kofoid and MacLennan. Adoral and dorsal 

 zones at anterior end; 2 skeletal plates beneath right surface; macro- 

 nucleus narrow; rod-like; 2 contractile vacuoles below dorsal surface, 

 separated from macronucleus. One species. 



D. affine (Dogiel and Fedorowa) (Fig. 309, e). 88-120/^ by 47-65^; 

 in the stomach of cattle, sheep, and goat. 



Genus Metadinium Awerinzew and Mutafowa. Adoral and dor- 

 sal zones at anterior end; 2 skeletal plates beneath right surface 

 sometimes fused posteriorly; macronucleus with 2-3 dorsal lobes; 

 2 contractile vacuoles; pellicle and ectoplasm thick; conspicuous 

 oesophageal fibrils beneath dorsal and right sides; in the stomach of 

 cattle, sheep, goat, and reindeer. 



M. medium A. and M. (Fig. 309,/). 180-272^ by 111-175^; in cat- 

 tle. 



Genus Polyplastron Dogiel. Adoral and dorsal zones at anterior 

 end; 2 skeletal plates beneath right surface, separate or fused; 3 

 longitudinal plates beneath left surface, with anterior ends con- 

 nected by cross bars; contractile vacuoles beneath dorsal surface in a 

 longitudinal row, also with additional vacuoles; in the stomach of 

 cattle and sheep. 



P. multivesiculatum (D. and Fedorowa) (Fig. 310, a). 120-1 90^ by 

 78-140/x; in cattle and sheep. MacLennan (1934) found that the 

 skeletal plates are made up of small, roughly prismatic blocks of 

 glycogen, each with a central granule. 



Genus Elytroplastron Kofoid and MacLennan. 2 zones at anterior 

 end, 2 skeletal plates beneath right surface, a small plate beneath 

 ventral surface, and a long plate below left side; pellicle and ecto- 



