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PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 55. 



appearing to have but one large tooth when examined under low 

 magnification; lower jaw of type VIII, teeth of the usual propor- 

 tions for that type ; anterior nephridia opening to the outside through 

 a common pore in segment III ; spermatheca simple, bulbous ; testes 

 in segments V and VI, vasa deferentia from segments V and VI 

 meeting in segment VI. 



Table 6. — Distribution of Branchiobdellids examined according to host. 



EXPLANATION OF PLATES, 

 Plate 10. 



Pig. 1. — Cross section of body of Xironogiton oregonensis orcgonensis Ellis, in 

 .«iegment V, showing the butress-like supports of the intersegmental 

 partition. The positions of these structures are indicated by the 

 dotted lines. AC=alimentary canal. 

 2. — Sagittal section of the head of Xironogiton oregonensis orcgonensis 

 Ellis, from Eugene, Oregon. 

 fl=first dorsal pharyngeal diverticulum. 

 ?/=second dorsal pharyngeal diverticulum. 

 c=veutral pharyngeal diverticulum. 

 d=lumen of the pharynx. 



c=false diverticulum formed by the contraction of the specimen during 

 fixation. 

 3. — Side view of type-specimen of Cambarincola. ritrca Ellis, from Douglas 

 Lake, ^Michigan. 



