FOREIGN DISTRIBUTION:—
Europe: France; (25): Spain; (12).
(2.) Able to roll up into a ball.
Genus—CYLISTICUS Schnitzler, 1853 (65), p. 24.
Flagellum, with two joints; abdomen broad; frontal lobe, very small.
The characters given immediately above are almost those of Porcellio with which Cylisticus might, perhaps, be confounded. The latter has the power, however, of rolling itself into a ball, and the first segment of the thorax is comparatively larger than in any species of Porcellio, indeed the side plates of the segment in question entirely flank the head. These features, as well as the straight sides of the body and the arched back, connect Cylisticus with Armadillidium, from which the former is, however, at once separated by its long pointed tail appendages.
Cylisticus convexus De Geer. [Plate XXI.]
1778 Oniscus convexus De Geer (10), p. 553, pl. XXXV., fig. 11.
1833 Porcellio spinifrons Brandt (3), p. 177.
1836 Porcellio laevis Koch (34), part 6, pl. I.
1853 Porcellio armadilloides Lereboullet (39), p. 65. pl. I., fig. 18.
1853 Cylisticus laevis Schnitzler (65), p. 25.
1868 Porcellio armadilloides Bate and Westwood (1), p. 485.
1898 Cylisticus convexus Sars (59), p. 186, pl. LXXXI.
There is but a single species of Cylisticus found in this country, so that it is not necessary for us to go into much further detail with regard to it. Cylisticus convexus has the two joints of the flagellum about equal, and they together in turn closely approximate in length to the last joint of the peduncle. Mr. Stebbing says, in a letter, that British examples do not appear to have the "white tail-piece" seen in Continental ones. It is not noticeable in the preserved specimens which we have seen from Berkhamsted and Leixlip, but it is very evident in the living ones found at Hanwell and Maidstone.