We are able to include this species, as a specimen was found by Mr. Webb at Eton Wick in the summer of 1899. It is one of a number of species which the Rev. Canon Norman (49, p. 18) suggested as likely to be British. It is the only representative of its genus, which does not differ in any very important characters from the others in the family. The narrow elongated body will serve to separate it from Trichoniscus vividus and Trichoniscus roseus, but on account of its size, which is much the same as that of Trichoniscus pusillus and the two British species of Haplophthalmus, it will be advisable to give some further points of distinction. From the first its white colour will serve to differentiate it; the other two lack the narrow abdomen seen in Trichoniscoides albidus. Moreover, not one of the three shows the serrations on the side plates which characterise the species under consideration. Platyarthrus hoffmannseggii is small and white and the edges of its side plates are toothed, but it is oval in shape, possesses no eyes, and its stout antennæ have but a single joint to the flagellum instead of four. On the Continent this species has been found in rich soil.
BRITISH LOCALITIES:—
England: Eton; (Stebbing, 71a): Sunderland; (Brady, 50a).
FOREIGN DISTRIBUTION:—
Europe: France; Wimereux and Lyons, Forêt (25): Norway; Denmark; (59).
Genus—HAPLOPHTHALMUS Schöbl, 1850 (66), p. 449.
Abdomen broad (comparatively); eyes simple; flagellum with three joints; back with longitudinal ridges.
The body of Haplophthalmus is long in proportion to its width, but there is no abrupt decrease in the breadth of the abdomen as seen in Trichoniscus and Trichoniscoides. The eyes are simple as in the latter genus and the lateral lobes of the head are rather large, while the side plates of the body are well separated.
Haplophthalmus mengii Zaddach. [Plate VII.]
1844 Itea mengii Zaddach (77), p. 16.
1860 Haplophthalmus elegans Schöbl (66), p. 449.
1885 Haplophthalmus mengii Budde-Lund (8), p. 250.
1898 Haplophthalmus mengii Sars (59), p. 167, pl. LXXIV., fig. 1.