NO. 2131. 



NEMATODE PARASITES OF RODENTS— HALL. 



91 



an elliptical structure to a point near the end of the body proper, 

 where the elliptical form terminates in an incision, the bursa then 

 expanding again to form a terminal bursal structure resembling, to 

 some extent, that of the strongyles. The bursa is supported by a 

 median extension of the cuticle forming a dorsal ray and by lateral 

 extensions forming lateral rays, one on each side. These three rays 

 diverge at approximately right angles from the posterior end of 

 the body. They tend to curve ventrally near their tips and the 

 lateral rays curve somewhat posteriorly near their tips. The rays 

 are approximately equal in length, ranging from 85 to 115 [/,. Near 

 the middle of the dorsal ray is a 

 transverse ridge on the dorsal as- 

 pect, with its distal edge directed 

 backward (fig. 113). Ventral of 

 the main copulatory bursa are two 

 ■s ymmetrically 

 disposed acces- 

 s o r y m e m - 

 1) r a n e s , each 

 supported by a 

 single wavy 

 ray. These 

 m e m b r a n e s 

 originate 



Fig. 110.— Oxyitris teiradiata. Head viewed 

 from tue front diagonally. x 340. 



lat- ^^^' 109-— OXYTKIS TRIRA 



"' DL\TA. Head. X 340. 



e r a 1 1 y at a 



point just posterior of the incision which divides the main l)ursa 

 into the rayed portion and the anterior elliptical portion. The 

 median insertion of these membranes is on either side of the l)lunt, 

 conical posterior termination of the body proper. Measured from 

 the anterior origin, these bursal membranes are 45 to 50 \i long. 

 Between their bases is a large papilla in the median line. At 

 a point slightly anterior of this papilla the posterior portion of 

 the body is protracted laterally to form two large papillae sug- 

 gestive of the prebursal papillae of the strongyles. The spicule 

 is a bluntly elongate conical affair, 43 to 52 fi long and 10 to 15 fi 

 thick at the base. It is usually not well chitinized, but may show 

 fairly heavy chitinous lines at the thick base. The cloacal aperture 

 is 115 to 138 fjL from the posterior extremity of the dorsal ray. 



Female 4.27 to 6.25 mm. long, with a maximum thickness, exclusive 

 of the dorso-ventral line through the greatly swollen lips of the 

 vulva, of about 430 fi. The head attains a maximum diameter of 

 75 to 80 fjL. The esophagus, exclusive of the esophageal bulb, attains 

 a maximum length of 400 to 415 /x and a maximum thickness of 75 to 



