Terrestrial nematodes from Jan Mayen Author Allgén, C. A. text Annals and Magazine of Natural History 1953 12 6 665 688 journal article 10.1080/00222935308654469 10811051 Mononchus papillatus Bastian. (Fig. 8.) Ba s tian, 1855 , p. 108, pl. x, figs. 52-53. Bütsehli, 1873 , p. 76, pI. iii, fig. 19 a~b. de Man, 1884 , pp. 64-65, pl. ix, fig. 35. Dimension s.- Body -length = 1.720 mm ., max. width=- 0.055 mm ., oesophagu s=0.4 9 7 mm ., tail= 0.148 mm ., vulva= l.088 mm., α= 3 1. 2 7, β =3.46, y =11.62, V = 63.26 per cent. Mono n chus papillatus Bastian. a, anterior end 1/12, ok. 3, x4 5 0. b, tail 1/12, ok. 3, × 4 5 0. 111 the sample from J2 was recorded a juvenile female o f the genus M o n o n c h u s Bastian, which in its general shape seems to agree rather well with M. l~apillatu~' Bast. This applies especially to the shape of the buccal cavity, which is ~u'med with a v e r y anterior dorsal tooth. The front end is e v i d e n t l y r o u n d e d b u t not bent o u t w a r d s as in the species of de Man (pl. ix, fig. 35). I t should bc mentioned t h a t the ventral wall of the buccal c a v i t y of the J a n M a y e n specimen is v e r y finely toothed. The ventral wall mostly is absolutely smooth, not toothed as in M. muscorum Duj. , closely related t o this species, a n d Bastian, who first described M. papillatus , also figured it in such a manner. Ditlevsen (1911) has, however, pointed o u t that Biitschli (1873) figured a h e a d of M. papillatus , the ventral wall o f the buccal cavity of which is evidently toothed, although not so strongly as in the alternative species. According to Mieoletzky it m a y sometimes, when the ventral wall is more strongly (sharply) toothed, be very difficult to separate this species from the old M. muscorum . I n this respect especially the structure o f the buccal cavity of the Jan Mayen specimen, the ventral wall o f which is evidently but more weakly toothed than in M. muscorum , seems t o agree rather well with the figure given b y Btitschli. Only the tail differs from this established cosmopolitan species, since it certainly tapers gradually posteriorly b u t seems to be a little more elongated and slender than in the type-specimen, figured b y de Man.