LIIST OF ILLUSTRATIONS. XI 



Page. 



Polytoreutus chaloneri. Section through esophageal pouch of somite, c, Eso- 

 phagus; e p, esophageal pouch 158 



Polytoreutus chaloneri. Longitudinal section reconstructed from several sec- 

 tions passing through the sperm duct and sperm vesicle, s c, Sperm cells; 

 sdf, epermiducal funnel; s m, sperm magazine; sp d, sperm duct; s s, open- 

 ing into sperm sac; stf, furcal branch of spermatheca; s v, sperm vesicle; sy, 

 epermary 158 



Polytoreutus chaloneri. Wax model reconstructed in part from sections showing 

 certain female reproductive organs, od, Oviduct; os, ovisac; st, median sper- 

 mathecal sac ; stf, furcal branch of spermatheca 160 



Polytoreutus multiporus. Ventral view of genital region, a st p, Accessory 

 Bpermathecal pores; g s p, modified setae and papillae; p, penis; st p, sper- 

 mathecal pore 162 



Polytoreutus viultiporus. Longitudinal section showing modified seta, g s, 

 Modified seta; p st, diverticulum of posterior branch of spermatheca 162 



Polytoreutus multiporus. Ordinary seta 163 



Polytoreutus multiporus. Longitudinal section showing the spermatheca near 

 the spermathecal pore, a st p, Most anterior accessory spermathecal pore at 

 19/20; b, edge of bursa; wc, nerve cord; si, posterior part of median sperma- 

 thecal sac; p st, posterior branch of spermatheca; st p, spermathecal pore 

 at 18/19 163 



Polytoreutus multiporus. Wax model reconstructed in part from sections 

 showing certain female reproductive organs, ovd, Oviduct; os, ovisac; p st, 

 part of posterior branch of spermatheca; st, median spermathecal sac; stf, 

 furcal branch of spermatheca 164 



Polytoreutus multiporus. Section through ovisac, o, Ovarian cells in different 

 growth stages; od, oviduct; os, ovisac; sk, diverticula of tie multicham- 

 bered samenkammerchen 165 



Sagital section through a tooth of the "B " order of the upper jaw of Xironogiton 

 oregonensis Ellis from Eugene, Oregon. Portion below AB, Anterior face; 

 Portion above DC, Supporting face, Portion below EF, Dental face; G, Base 

 of jaw; H, Dental ridge 241 



Hypothetical jaw. AC, Teeth; G, Base of jaw; H II, Dental ridge 242 



Upper jaw of type-specimen of Xironodrilus formosus Ellis, from Anderson, 



Indiana 245 



Lower jaw of type-specimen of Xironodrilus formosus Ellis, from Anderson, 



Indiana 245 



Upper jaw of Xironodrilus pulcheirimus, from Queens, West Virginia 246 



Lower jaw of Xenodrilus pulcherrimus 246 



Upper jaw of type-specimen of Xironogiton ocddentalis Ellis, from Crab Creek, 

 Washington 249 



Lower jaw of type-specimen of Xironogiton ocddentalis Ellis, from Crab Creek, 



Washington 249 



Upper jaw of type-specimen of Xironogiton oregonensis oregonensis Ellis, from 

 Eugene, Oregon 251 



Upper jaw of type-specimen of Xironogiton oregonensis pcctinatus Ellis, from 



Sequallitchew Lake, Washington 251 



Lov/er jaw of type-specimen of Xironogiton oregonensis pectinatus Ellis, from 



Sequallitchew Lake, Washington 251 



Upper jaw, anterior view of type-specimen of Pterodrilus durhini rCllis, from 



Anderson, Indiana 255 



LoAver jaw of type-specimen of Pterodrilus durhini Ellis, from Anderson, 



Indiana 255 



