652 THE AMERICAN NATURALIST. 
A. Posterior end not noticeably enlarged. Gordius, ? 9. 
a. We elevated cuticular areoles on the whole surface of the body. 
. With paired dark stripes in the median lines. G. Zeidyi 
(Montg.), 9 
2. No dark stripes in the median lines. 
a. Areoles elongated in the long axis of the body, well sep- 
arated from one another. G. longareolatus (Montg.), 9. 
6. Areoles not elongated in the long axis of the body. 
1. Areoles closely apposed, tending to produce longitudinal 
ridges. G. lineatus (Leidy), ? 
2. Areoles more or less confluent, tending to produce 
transverse rows; head usually cylindrical. ; 
densareolatus (Montg.), 
3. Areoles usually separated, interareolar groups of fine 
hairs, head usually flattened. G. platycephalus 
6. Without ne tee areoles on the whole surface of the 
ody. 
1. No cuticular areoles. 
a. Cuticle marked with white spots. G. aguaticus (Linn.),9. 
6. Cuticle without white spots. G. a. robustus (Leidy), 9 
2. Cuticular areoles at the ends of the body only. G. a. 
difficilis (Montg.), Ẹ 
B. Posterior end swollen, soniewhat knob-shaped, slightly constricted 
off. Chordodes, 9 9 
a. Cuticular areoles longer than high, on and between them small 
circular pits. Chordodes occidentalis (Montg.), 9 
6. Cuticular areoles higher than long. 
I. Spines on the summits of the highest areoles. C. puerilis 
(Montg.), 9 
2. No spines on the summits of the highest areoles. C. mor- 
gant (Montg.), 2 
