22 



mounted b}' an arched chitinous shield, appearing in side 

 view like a hood, armor either arched and compressed, open 

 behind and in front [Co/iiir/la, fig. 27), or of equal height 

 and width or depressed, not open ventrally {3Ietopia). 



COLURELIvIDiE. 



jj. With other characteristics. 



k. Armor of two dissimilar plates, one dorsal and one ventral, 



the former larger and arched (except in one species), the 



latter flat or slightly convex ; large transparent rotifers with 



a single eye ; foot jointed, the two toes large, usually blade 



shaped, (fig. 25). Euchi^anid.^, Euchlanis. 



kk. Armor of a different structure. 



I. Armor with two or four spines on posterior margin ; head 



without shield ; either anterior margin of armor with two 



spines (Noteus quadricornis) or with ten spines (N. mili- 



taris) or dorsum with one (B. gleasonii) ; foot distinctly 



jointed ending in one or two toes. Brachionid^. 



m. Armor (not including length of spines) as long as broad or 



but little longer, smooth, granulate, or with polygonal 



areas. 



n. Foot simple, conical, not jointed, at most transversely 



wrinkled (fig. 30). Brachionus. 



nn. Foot distinctly three jointed (fig. 32). Noteus. 



mm. Armor (not including the spines) much longer than 



broad, always smooth. Schizocerca. 



II. Foot and toes usually very long, or if not, dorsum of armor 



with long spines or head with distinct shield. 



DlNOCHARlD.^;. 



m. Armor flattened and bearing one or more spines on its 



dorsal surface, eyes one or two ; if not spined then two 



eyed and with broad, nearly circular projecting plate 



over head, halo-like, and armor cylindrical or pyriform. 



n. A single median eye. Polychcctus. 



nn. Two eyes. Stcphanops. 



mm. Armor not bearing spines on dor.sal surface, entire (not 



cleft dorsally and ventrally) vase .shaped or compressed, 



eye one ; foot ver}' long. 



n. Head retractile, with a chitinous cap ; foot bearing two 



spines dorsally ; foot and toes together nearly or quite 



twice as long as the body ; armor facetted, and surface 



roughened (fig. 22). Dinocharis. 



nn. Head with thin chitinous covering ; armor vase shaped, 



thin, smooth, and transparent. Scaridimn. 



ee. Foot absent. 



f. Armor oval compressed, without teeth or spines ; head with long 



finger-like processes (fig. 40). Anapodid.-i;, Anapus. 



ff. Armor u.sually with teeth or spines ; head without finger-like pro- 



ces.ses. Anur.Eid.'E. 



g. Anterior margin of armor with six s])ines. 



