Mononchus papillatus Bastian.

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.

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.