6 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 78 



the cloaca, very inconspicuous. Spicules unequal, the shorter one 

 chitinized and trough-shaped for about three-fourths of its length, 

 at which point it has an elbowlike projection; terminal portion mem- 

 branous and very delicate; chitinized portion of spicule 75/x, to 80fx 

 long, total length, to end of membranous tip, lOO/x, to 105/i. Long 

 spicule with total length of 185/x to 295/x ; proximal two-fifths trough- 

 shaped, chitinized, followed by an apparent break, then a portion 

 partly chitinous and partly membranous, ending finally in a delicate 

 filament. 



Female 50 to 65 mm. long, with a maximum diameter of about 

 oOOju, to 325/x. Vulva situated about 1.25 mm. from anterior end, 

 about twice the length of the esophagus behind the anterior end of 

 the worm. Vulva opens into a large, muscular, bulblike structure, 

 from which a thick-walled muscular vagina, nearly 1 mm. in length, 

 continues backward, and in many specimens loops forward again 

 before changing to a thin-walled tube filled with embryos. The 

 latter tube remains single for a length of about 300/a to 400ju, before 

 splitting into the two uteri. The latter continue almost to the anus 

 as nearly straight tubes, only slightly convoluted by forward loop- 

 ings. Tail very slender, terminal half with almost parallel sides, 

 rounded at tip, about 625/x long. 



Embryos in uterus about 100^ to 105/^ long, unsheathed, with 

 pointed tails. 



Hosts. — Sigmodon hispidus, and white rat. 



Location. — Thoracic cavity. 



Locality. — Houston, Tex. 



Type specimens. — United States National Museum helminthologi- 

 cal collections, No. 8100, paratypes No. 8101. 



This species is very close to Filaria circularis von Linstow, 1899, 

 described from another rodent, '"'' Hesperomys sp.f'' from Porto 

 Alegre, Southern Brazil, which now becomes Litomosoides circularis 

 (von Linstow, 1899). Von Linstow's species differs from L. sig- 

 modontis in a number of details, particularly in being relatively more 

 slender, in the shorter tail of the male, in the presence of seven in- 

 stead of four postanal papillae, and in the different size of the 

 spicules. L. sigmodontis occurs in a high percentage of cotton rats in 

 the vicinity of Houston and was found also in a white rat born and 

 raised in the Rice Institute animal house, where some infected cotton 

 rats were kept. 



FILARIOPSIS ARATOR, new species 



Figures 8, 9, and 10 



Spedfo diagnosis. — Filariopsis : Body slender and cjdindrical, 

 with bluntly rounded extremities. Cuticle smooth with traces of 

 very fine striation, but provided with an irregular, transparent excre- 



