TRICHOSTRONGYLIN^ 



273 



171.1. 



Fig. 142. — Ostertagia ostertagi. 

 Posterior extremity of male with 

 bursa spread out: d, dorsal ray; e. d., 

 externo-dorsal ray; p. 1., postero- 

 lateral ray; m. 1., medio-lateral ray; 

 o. 1., externo-lateral ray; 1. v., latero- 

 ventral ray; v. v., ventro-ventral ray; 

 p. b. p., pre-bursal papilla; sp., spi- 

 cules. . xl50. (After Ransom, from 

 Railliet, Bull. No. 127, Bureau An. 

 Ind., U. S. Dept. Agr.). 



Fig. 141. — Ostertagia oster- 

 tagi; male at riglit, female at 

 left. * Vulva. xl5. (After Ran- 

 som, Bull. No. 127, IBureau An. 

 Ind. U. S. Dept. Agr.). 



by a prominent cuticular flap; it is located 

 close to the caudal extremity of the body. 

 The tail tapers gradually and ends in a slen- 

 der tip. 



Length of female, 8-10 mm. (5/16-3/8 of 

 an inch) ; male, 7-8 mm. (1/4-5/16 of an inch.) 



The eggs are oval, 65-80 microns in length 

 by 30^0 microns in breadth. 



The worm is parasitic in the wall and cavity of the abomasum of 

 cattle. 



2. Nematodirus filicoUis (Strongylus filicollis). Fig. 143. Tricho- 

 strongylinse (p. 268). — This is a white hair-like worm, very thin in front, 

 thicker behind. The cuticle has eighteen longitudinal ridges. The 

 bursa of the male is bilobate; there are two very long and slender spicules 

 united by a membrane posteriorly which forms a spatulate enlargement 

 at the tip. The vulva of the female is a transverse slit located about 

 one-third of the length of the body from the caudal extremity. At this 

 location the body has its maximum thickness which is suddenly reduced 



