242 



TROCHELMINTHES 



M. bulla Gosse (Fig. 393). Dorsal plate very high; ventral plate 

 somewhat convex; anterior margin with a notch; .25 mm. long: very 

 common among aquatic plants. 



Fig. 393 



Monostyla bulla 



(Jennings). 



Family 7. EUCHLANIDAE. 



Large transparent rotifers with a convex dorsal and 

 a flat or slightly convex ventral plate ; foot jointed, with 

 2 large, diverging, blade-shaped toes: 2 genera. 



EuCHLANis Ehrenberg. Lorica oval and flat; eye 

 present: 7 species. 



E. dilatata Ehr. (Fig. 394). Lorica with a pair 

 of lateral flanges projecting from its ventral plate; 

 anterior dorsal margin with a broad gap having a 

 straight bottom; length .3 mm.: often very common in 

 aquatic vegetation. 



Family 8. COLURIDAE. 



Head surmounted by an arched shield, appearing in a side view like 

 a hook: 5 genera. 



1. Metopidia Ehrenberg. Lorica flattened, usually turtle-like in 

 appearance; usually 2 eyes: 11 species. 



M. lepadella Ehr. (Fig. 395). Lorica oval, without teeth or spines 



Fig. 394 



Fig. 395 



Fig. 396 



Fig. 394 — Euchlanis dilatata (Siissw. F. Deut). Fig. 395 — Metopidia lepadella 

 (Siissw. F. Deut.). Fig. 39G — Monura colurus (Hudson and Gosse). 



or prominent angles; 2 eyes; ventral plate indented behind; length .08 

 mm. : often abundant among aquatic plants. 



M. acuminata Ehr. Lorica oval, ending behind in a sharp point; 

 length .08 mm.: often common among aquatic plants. 



2. MoNXTRA Ehrenberg. Lorica arched, more or less compressed lat- 

 erally, often open mid-ventrally. 



M. colurus Ehr. (Fig. 396). Length .1 mm.: often common among 

 algae in the sea. 



