No. 417.] 
NORTH-AMERICAN INVERTEBRATES. 741 
the ventral surface as a large movable ciliated « lip 
(except in Nos. 99, 100, and 101); body projecting back- 
ward over the foot as a jointed or sac-like tail; auricles 
usually present ^, isi 7. . 4. Copeus 
Ar. The two toes alike 
zz. "Tailslender, usually pointed, prominent, obscurely 
two-jointed ; foot two-jointe 
ji. Auricles very long (longer than the width of 
the head), extending laterally, ciliated yd at the 
tip and along the anterior side . 97, C. copeus, 
Ehr. (or C. ehrenbergii Gosse) (Fi ig. 69) 
j2. Auricles very small or absent 
98, C. labiatus Gosse 
(97 and 98 are probably identical, 98 being founded 
on specimens of 97, with the auricles retracted) 
22. Tail thick, rounded, bag-like; auricles large, 
broadest at base 
jr. Brain three-lobed . . . 99, C. pachyurus 
Gosse (Fig. 70) 
j2. Brain five-lobed . . 100, C. guinguelobatus 
Stokes 
(Probably a variation of 99) 
73. Tail small, inconspicuous; brain three-lobed 
ji. Tail a minute tubercle; corona without lip ; 
auricles very small ; toes very small 
1o1, C. cerberus Gosse (Fig. 71) 
A2. The two toes dissimilar in form; tail slender, 
rounded ; no lip 102, C. americanus Pell (Fig. 72) 
42. Moderate-sized or small (except No. 106); auricles 
present; toes small; brain usually partly opaque, not 
three-lobed ; body ss d RR behind, above the 
foot, as a large or small “ tail” . Notommata 
(A difficult genus with very numerous species, — many of the 
American ones not yet identifie 
Ar. Tail long, almost or quite as long as the toes, so 
that the animal seems to end caudally in three 
prominent toes. . . 103, JV. tripus Ehr. (Fig. 73) 
A2. Tail inconspicuous or absent 
ir. Brain clear ; body fusiform; head narrower than 
the body ; auricles small; toes minute cones ; foot 
very short . 104, W. drachyota Ehr. (Fig. 74) 
72. Brain more or less opaque 
jz. Color orange red or brick red, with a brownish 
tinge; body long, cylindrical, truncate at each 
end ; cilia extending onto ventral surface almost 
