EXPLANATION OF PLATES 



All drawings were made from stained permanent mounts in 

 clarite, by aid of a camera lucida. Katharine Hill Paul, scientific 

 artist in the department of zoology of the University of Illinois, 

 prepared the drawings and arranged the plates. 



Symbols Used 



a, anus It, lateral excretory trunk 



ac, acetabulum mt, median excretory trunk 



ace, anterior cecum o, egg 



ap, acetabular papilla ol, oral lip 



as, anterior sucker os, oral sucker 



ca, cecal arm ov, ovary 



cir, cirrus ph, pharynx 



cs, cirrus sac pv, prostatic vesicle 



e, esophagus sr, seminal receptacle 



es, eye spots sv, seminal vesicle 



ex, excretory vesicle t, testis 



ga, genital atrium ut, uterus 



gp, genital pore v, vitellaria 



ic, intestinal cecum yr, yolk reservoir 



Plate 12 



1, 2. Bucephalopsis labiatus, new species: 1, Holotype as viewed from ven- 

 tral surface; 2, lateral view of pharynx and oral lip as seen in a 

 paratype individual. 



3-5. Opecoelus adsphaericus, new species : 3, Holotype as viewed from right 

 side; 4, acetabulum of a paratype as viewed from lateral surface to 

 show papillae, one pair of the lateral papillae not shown; 5, region 

 of genital atrium showing relations of ducts to other structures. 



6,7. Pseudopecoehis gibbonsiae, new species: 6, Holotype in side view; 

 7, detail showing structures associated with the genital atrium. 



8, 9. PseudopecoeliLS umbrinae, new species : 8, Holotype as viewed from 

 ventral surface; 9, relations of genital ducts to the genital pore in 

 a paratype individual. 



Plate 13 



10. Helicometrina elongata Noble and Park, 1937, viewed from the ventral 

 surface. Specimen from intestine of Clinocottus analis australis. 

 11, 12. Opechona orientalis (Layman, 1930) Ward and Fillingham, 1934: 11, 

 Entire worm chiefly from ventral view; 12, detail of posterior ex- 

 tremity showing relations of the excretory trunks and vesicle. 



13. Stephanostomum calif ornicum, new species : Morphology of holotype. 



14. Pleorchis calif omiensis, new species: Holotype as viewed from dorsal 



surface. Only the dorsal series of testes is shown. 



15, 16. Diplangus triradiaUis, new species: 15, Holotype in side view; 16, An- 

 terior extremity of a paratype, showing details of structure. 



17,18. Haplosplanchnus girellae, new species: 17, Holotype in lateral view; 

 18, a single uterine egg. 



340 



■ft U. S. GOVERNMENT PRINTING OFFICE; 1950 899I3S 



