NO. 2131. NEMATODE PARASITES OF RODENTS— HALL. 125 



Males less than 7.5 rum. long ; females less than 10 mm. long ; spicules less 

 than 500 /a long ; vulva less than 2 uuu. from the end of the tail ; anus less 

 than 150 /j. or else 1 mm. or more from the end of the tail ; viscera not 

 pigmented black 3. 



3. Dorsal ray originates asymmetrically from the base of the right externo- 



dorsal ray ; spicules 175 fi long or longer ; vulva 1 mm. or less from the 



tip of the tail T ricliostrongylus calcaratus, p. 126. 



Dorsal ray symmetrical throughout; spicules less than 175 fi long; vulva 

 more than 1 mm. from the tip of the tail 4. 



4. A small dorsal lobe present in bursa ; males over 5 mm. long ; spicules less 



than 125 fi long; vulva more than 1.5 mm. from the tip of the tail; anus 

 1 mm. or more from the tip of the tail. 



T ricliostrongylus retortneforrnis, p. 125. 



No dorsal lobe present in bursa; spicules more than 125 fi long; vulva less 



than 1.5 mm. from the tip of the tail ; anus less than 1 mm. from the 



tip of the tail T ricliostrongylus delicatus, p. 130. 



TRICHOSTRONGYLUS RETORTAEFORMIS 

 (Zeder, i8oo) Looss, 1905. 



r c'tortae- 



FlG. 151.— TRICHOSTRONGiaXIS RETOR- 

 TAEFORMIS. Bursa. X 150. After 

 Railliet, 1895. 



/Synonym. — Strongyliis 

 formis Zeder, 1800. 



Sj)eciiic diagnosis. — Trichostrongy- 

 lus (p. 124) : Body capillary, very much 

 attenuated anteriorl3^ Head some- 

 what inflated at times. 



Male 5.5 to 7 mm. long with a maxi- 

 mum body thickness just anterior of the 

 spicules of 60 [x.. The bursa (fig. 151) 

 is deeply incised in the middorsal line 

 forming two large lateral lobes and a 

 very small dorsal lobe. The latero- 

 ventral ray is quite thick and the 

 lateral rays diminish from the straight thick externo-lateral to the 

 thin postero- lateral, the last named being close to the externo-dorsal 

 ray. The tip of the externo-dorsal ray is about halfway between 

 the tips of the postero-lateral and the dorsal rays. The dorsal ray 

 divides close to the bursal margin to form two short branches, each 

 of which ends in a double point. The short thick spicules are 100 to 

 110 /A long and appear twisted as a result of ridges. Viewed from 

 the side the posterior edge of the spicules is slender and smooth 

 edged. The gubernaculum is boat-shaped and is G3 /x long. Spicules 

 and gubernaculum are dirty brown in color. 



Female 6 to 7.7 mm. long and 80 to 90 /x thick in the region of the 

 vulva. The tail graduall}' narrows from the point where the pos- 

 terior uterus bends forward, and is prolonged in a conical point. 

 The anus is only slightly salient and is 1 to 1.2 mm. from the tip of 

 the tail. The vulva aperture is short and often crescentic and is 1.8 



