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PROCEEDINGS OF THE NATIONAL MUSEUM 



VOL. 79* 



where the tail narrows in diameter is much less conspicuous in P, 

 nonanulatus than in P. amUguus. No caudal alae are present in 

 P. nonanulatus. 



Figures 12-lQ. —Metathelazia californica: 12, Anterior end of male, showing 

 cervical serrations; 13, head of male, en face view; 14, anterior end of male; 

 15, egg; 16, anterior view of head, showing the quadripartite condition in the 

 region of the vestibule ; 17, anterior half of male, showing loop in the testis ; 

 18, posterior end of female, showing vulva and anus, lateral view ; 19, posterior 

 end of male, lateral view 



