AKT. 15 NEW NEMATODE FItOM THE RAT CRAM 6 



pointed. The sheath of the longer spicule is strongly developed; 

 when the spicule is extruded the sheath is compressed accordion- 

 like, its numerous ridges or folds being seen clearly through the 

 body wall Avhen the specimen is cleared, whereas when the spicule 

 is completely drawn into the body the sheath is extended so that 

 its walls are smooth. There is a distinct telamon present, sharply 

 limiting the cloacal aperture; it appears to be horseshoe shaped, 

 the open ends directed anteriorly. 



Female. — Total length 45 to 100 mm.; wadth 800^ to 2.4 mm. 

 In a specimen of medium size the width of head at base of lips is 

 265j(x, the pharynx 215ju, long, its lumen 66/i in diameter, its walls 

 17/x thick. Esophagus 0.4 mm. long (^V of total body length), the 

 nerve ring 250/x from its anterior end. Uterus extends anteriorly 

 to a point 1.7 mm. posterior to the junction of esophagus and intes- 

 tine. Caudal extremity bluntly rounded, the cuticle thrown in loose 

 folds. The anus is not situated at the level of the superficial cuticle 

 but at the bottom of a channel formed by a prepucelike sheath. The 

 anus is 750/i, to 1.2 mm. from tail end whereas the opening of the 

 sheath is 400 to 580/a from the extremity. Vulva inconspicuous, 

 situated slightly anterior to middle of body, dividing the body 

 length in ratio of 4:5. The posteriorly-directed vagina, 531jtt long, 

 is followed by a slightly enlarged sphincter, 183/1 long, and that by 

 the unpaired portion of the uterus which after a length of 1.6 mm. 

 divides into the two divergent uterine branches. Eggs 52 to 58ft 

 by 30 to 33ju; the embryo, measured after being released from the 

 shell, 232/>i long by lOfi wide, with a small knob bearing minute 

 spines at its tail end. 



A male and female were observed in copula (fig. 9), the posterior 

 end of the male being tightly coiled around the body of the female, 

 in the region of the vulva. The tight clasp constricts the female 

 bod}' very decidedly anterior to the vulva and suggests that its 

 purpose may be not only to secure the female but possibly to dilate 

 the vulva and vagina. 



Fourth-stage larva (fig. 13) G.G mm. long by 257/x wide to 11.5 mm. 

 long by 300/>i wide; first part of esophagus 150/x, second part of 

 esophagus 3.3 mm. long; anus 216;(x from tail end. 



Host. — Rattus norvegicus. 



Location. — Stomach and, occasionally, esophagus and anterior end 

 of small intestine. 



Locality. — Washington, D. C. 



Type material.— ^o. 26383, paratypes No. 26384, U.S.N.M. 

 (Bureau of Animal Industry) Hclminthological Collections. 



Life history. — On October 2, 1924, a culture was made in physio- 

 logic saline solution of embryonated eggs from the uteri of several 

 worms and fed on bread to several cockroaches (crot(m bugs or 



