246 
Nematodes in Sheep 
posterior end of the body. The tail is slender and its posterior portion 
marked with faint annular striations. The eggs in the uterus measure 
60-80 fjL long by 30-40 /x wide. 
8. Nematodirus filicollis Rudolphi. 
{Strongylus Rudolphi.) 
This species was found to be one of the commonest parasites of the 
alimentary tract, occurring in large numbers in the small intestine of 
sheep and lambs both at Birmingham and Wye. 
According to Railliet and Henry (1912), there has been much 
confusion between this species and the closely allied N. spathiger 
Railliet, the worms described by Ransom belonging to the latter 
species. All the specimens of Nematodirus which I have examined 
belong to the speciesdiffering from N. spathiger in the absence 
of the dorsal lobules of the bursa and in the shape of the terminal * 
membrane of the spicules which is lanceolate, not spatulate. 
9. Trichostrongylus instabilis Railliet. 
I have only met with a single specimen of this worm, a male 
4-2 mm. long found together with T. extenuatus in the intestine of a 
lamb at Tenbury. The spicules measure 130 p, in length and agree very 
closely with those figured by Looss (1905) and Ransom (1911). (Cf. 
Fig. 3.) 
10. Trichostrongylus vitrinus Looss. 
A common parasite of the small intestine and fourth stomach of 
sheep at Birmingham and Wye. I do not know of any previous 
records of its occurrence in England, where it has probably been con¬ 
fused with T. extenuatus. From the other species of Trichostrongylus 
it is easily distinguished by the large size of the bursa and spicules, 
the latter being more than 160 p- long. The shape of the spicules is 
also very characteristic, ending in sharp points without hook-like 
projections (Fig. 4). 
Some of my specimens of T. vitrinus are somewhat larger than 
those described by Looss and Ransom, the males measuring 4-5-6-3 mm. 
in length, the females 5-5-7-2 mm. The male bursa has a width of 
300-350 p., whilst the spicules vary between 160 and 180 p.. The 
