A brief description of Nematodirus battus has been given elsewhere (Crofton and Thomas, 1951), but this included only sufficient details for specific diagnosis. A more detailed account is given below.

The worms are long, slender and more or less straight. The cuticle is smooth except in the cephalic region where it is inflated and is lightly striated. The cephalic inflation extends 0.12 mm. from the anterior end and is 0.06 mm. in diameter (see Fig. 1). In some specimens the cephalic inflation may be reduced and relatively inconspicuous. Although this variation may be due to fixation, it occurs in members of a batch which have been fixed simultaneously. The head is 0.03 mm. in diameter and bears six papillae round the mouth. The “mouth capsule” is small and bears a tooth on the dorsal side. This tooth is not easily visible in Fig. 1 because of contraction of the oesophagus. (The term mouth capsule is retained because it has been used by other workers (see Rajewskaja, 1918, Travassos, 1987) but if the definitions of Baylis and Daubney (1926) are adopted it would be more correct to refer to the tooth as lying in an oesophageal funnel). The oesophagus is relatively short, 0.35–0.54 mm. in length.