56 ILUNOIS BIOLOGICAL MONOGRAPHS [160 



EXPLANATION OF PLATES 

 Plate I 



Fig. 1. Oxyuris obvdata. Head of a female en face showing the 3 lips and the 6 papillae 



disymmetrically arranged. After Flogel. X6S0. 

 Fig. 2. Ter otocephalus crassidens. Lateral view showing the peculiar flanged lips. After 



deMan. X220. 

 Fig. 3. Mononchus gcrlachei. Head en face showing the 6 partially fused lips, the pharyngeal 



armature, the large dorsal tooth and the superficial radial symmetry. After de 



Man. X600. 

 Fig. 4. Same as in Fig. 2, dorsal view. After de Man. X220. 

 Fig. 5. Anguillida aceli. Head of female en face, showing fused lips and hexagonal mouth 



opening. After de Man. X12S0. 

 Fig. 6. Cephalobus cUiatus. Showing the peculiar prolongations of the lips. After de Man. 



X220. 

 Fig. 7. Jointed mandibles of Scaptrdla cincta infleied and extended. After Cobb. X550. 

 Fig. 8. Optical cross section of the posterior portion of buccal cavity of a growing female, 



Anguillida aceti. After de Man. X1900. 

 Fig. 9. Cross section of pharynx of Mononchus muscorum showing the sutures and the dorsal 



tooth. After Cobb. X400. 

 Fig. 10. Head of Prolospirura muris showing the disymmetry of the two tri-partite lips. 



Original X200. 

 Fig. 11. Jointed cephalic seta. After Cobb. 

 Fig. 12. Lateral optical section of Monochus macrostoma, showing spacious pharynx and large 



dorsal tooth. After Cobb. X400. 

 Fig. 13. Head of Monhystera piJosa showing the delicate cephalic bristles. After Cobb. 

 Fig. 14. Head of a growing female of Anguillula aceti, showing the break in the pharyngeal 



wall between upper and lower sections. After de Man. X 1250. 



