NO. 2131. 



NEMATODE PARASITES OF RODENTS— HALL. 



157 



originate about two-thirds of this distance. The bursal areas between 

 the rays are marked with irreguhir macidae, following in a genera! 

 way the contour lines of the rays. This marking results in a certain 

 opacity, with the result that the rays commonly appear as light lines 

 against a darker and more opaque background, contrary to the usual 

 condition in the strongyle bursa, where the rays are usually more 

 opaque than the bursal membrane. The 

 simple, filiform spicules are oGO to 440 fi 

 long. 



Female 3.44 to 4.37 mm. long and with a 

 maximum thickness of about 00 jx. The 

 head diameter is about 25 /i. Esophagus 

 is 275 to 290 /x long, with a maximum thick- 

 ness of about 30 ju,. Nerve ring about 110 

 fi from the anterior end of the body. The 

 intestine is straight. The rectu.m is a nar- 

 row cylindrical to elongate conical struc- 

 ture about 25 IX long. The anus is 34 to 42 

 fi from the tip of the tail. The tail is coni- 

 cal and shows the transverse striation 

 prominently. The vulva is 122 to 127 /x 

 from the tip of the tail (fig. 204), and on 

 the dorsal side opposite the vulva is often 

 a projecting cuticular structure. The ovi- 

 jectors are not well preserved in my mate- 

 rial, and I am unable to give any details of structure. The single 

 uterus has few eggs, commonly three to nine, in it. The eggs are 

 oval, about 70 by 32 fx in diameter. 



HO'Sf. — Tliomomiia fosso)\ 



Location. — Small intestine. 



Locality. — Livormore (Larimer County), Colorado. 



The refractive granules in the intestinal wall are evidently similar 

 to the rhabditin described by Cobb (1914) from Rhahditls monhyS' 

 tera and to the refractive nuclei found by V(m Linstow (1882) in 

 what he regards as Heligmosomum minutum. It is interesting to 

 note that all these species are forms with one ovary and that Leuckart 

 has established the presence of the rhabditifoi-m embryo for a species 

 of LLeliginosomuin. It suggests that the presence of the interesting 

 nutritional granules studied by Cobb will probably be demonstrated 

 in a much larger number of allied parasitic and nonparasitic forms 

 on further investigation. 



Tyi)e material. — No. 1G142, U.S.N.M. (Bureau of Animal Industry 

 helminthological collection) . 



204. — Heligmosomum vexil- 

 LATUM. Female. 



