342 ILLINOIS BIOLOGICAL MONOGRAPHS [342 



EXPLANATION OF PLATE 



Fig. !33- — Proteocephalus fossatus (Riggenbach), head, toto. After Riggen- 

 bach. 



Fig. 134a & b. — Proteocephalus ambloplitis (Leidy), head (a) and part of stro- 

 bila (b). After Leidy. 



Fig. 135. — Proteocephalus exiguus La Rue, entire worm. After Benedict. 



Fig. 136. — Proteocephalus exiguus La Rue, entire worm. After Benedict. 

 These two figures show the variation in length of neck. 



Fig. 137. — Proteocephalus exiguus La Rue, head, frontal section. After Bene- 

 dict. Shows structure of the functional fifth sucker. 



Fig. 138. — Proteocephalus exiguus La Rue, head, toto showing fifth sucker. 

 After Benedict. 



Fig. 139. — Ophiotacnia nattereri (Parona), head, toto. After Schwarz. 



Fig. 140. — Ophiotacnia racemosa (Rud.), head, toto. After Schwarz. 



Fig. 141. — Ophiotacnia trimcresuri (Parona), head, toto. After Parona. 



Fig. 142. — Ophiotacnia trimcresuri (Parona), head, toto. After Parona. 



Fig. 143. — Proteocephalus salvclini (Linton), head, toto. After Linton. 



Fig. 144. — Proteocephalus salvelini (Linton), head. After Linton. 



Figs. 145, 146. — Proteocephalus torulosus (Batsch), heads, toto. After Batsch. 



Figs. 147, 148. — Proteocephalus dubius La Rue, heads, toto. After Zschokke. 



Fig. 149. — Proteocephalus dubius La Rue, proglottid. After Zschokke. 



Fig. 150. — Proteocephalus fallax La Rue, head, toto showing fifth sucker. After 

 Kramer. 



Fig. 151. — Choanoscolcx abscisus (Riggenbach), head, toto. After Riggenbach. 



Fig. 152. — Proteocephalus skorikowi (von Linstow), head, toto. After von 

 Linstow. 



