No. 431.] MORTH-AMERICAN INVERTEBRATES. 899 
m,. Yolk glands extend forward of the acetabulum. 
7. Testes not in same transverse plane; cirrus sac ex- 
tends back of acetabulum : inamphibians, reptiles, 
and birds — Plagiorchis Lühe (Fig. 48) (50, 10) 
a Testes in same transverse plane. 
o. Cirrus sac extends far back of acetabulum: 
in turtles Pachypsolus Lss. (Fig. 49) (49) 
0, Cirrus sac extends to middle of acetabulum; 
body divided into two parts : in crocodiles 
Oistosomum Oldh. (71) 
m,. Yolk glands do not extend in front of acetabulum; 
body elongate, tapering to posterior end, which is 
truncated: in fish — Glossidium Lss. (Fig. 50) (44) 
4. CEsophagus present. 
74. Body covered with minute spines or scales. 
7. Testes not in same transverse plane. 
o,. One intestinal coecum much longer than the 
other; testes elongate ; a single row of 
spines around mouth: in fish 
Subfamily VII. Anisocceline 
f, Testes very small, in center of body ; ovary 
lobate; uterus does not extend to end of 
intestinal coeca 
Anisoceelium Lühe (Fig. 23) (52) 
f, Testes in hinder half of body; ovary 
sp ean uterus extends to end of body 
nisogaster Lss. (Fig. 24) (48) 
2,. Intestinal coeca $^ equal length. 
Pi Oral un mper m et im 
, stem of CAT 

cretoty vesicle very long, winding between 
testes ; receptaculum seminis minute ; cir- 
rus sac long : in aquatic vertebrates 
Astiotrema Lss. (Fig. 51) (44. 45) 
f, Oral sucker smaller than acetabulum; yolk 
glands do not extend in front of latter ; 

stem of excretory vesicle short : inreptiles 
typhlodora Lss. (Fig. 52) (44, 77) 
t Testes in nearly or quite the same transverse plane 
and lobate ; oral sucker smaller than acetabulum ; 
yolk glands extend about to acetabulum ; recep- 
taculum seminis absent or minute ; ; stem of 
emm vesicle very long: i 
Renifer Pratt it (Fig. 53) (77) 
