There are granulations on the middle of the segments in _Porcellio ratzeburgii_ and the sides of its body are more nearly parallel than in the other species of _Porcellio_; the frontal lobe is, practically speaking, semicircular and the lateral plates of the thorax flank the head to a considerable extent. As in _Porcellio pictus_, the dark band is in the middle of the back. The distal joint of the flagellum is nearly twice as long as the proximal, and the flagellum is shorter than the last joint of the peduncle. This species was added to the British list by Mr. Webb (74) in 1898. _Porcellio ratzeburgii_ agrees with _Porcellio rathkei_ in having air-tubes in the first five abdominal appendages. [Illustration: FIG. 52.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE ANTENNA OF _Porcellio ratzeburgii_.] _BRITISH LOCALITIES:--_ _England_: Warley; Brightlingsea; young examples (W.M.W.): Maldon; young examples (W.M.W. from R.M.) _FOREIGN DISTRIBUTION:--_ _Europe_: Trafoi St. Martini, and Capitello, in the Tyrol; (Norman, 50); East Alps, very common; Val-de-Joux; Massif de la Chartreuse Vaulnaveys (25): Bosnia; (22): Norway; Central Europe; Upper Pfaltz; Bohemia; Saxony; Rhaetia; (59). _Genus_--=METOPONORTHUS= Budde-Lund, 1879 (7), p. 4. _Porcellionides_ Miers, 1876 (44), p. 98. _Flagellum, with two joints; abdomen, narrow; frontal lobe not developed._ The hinder legs of _Metoponorthus_ are proportionately longer than in any other Oniscidæ save _Philoscia_. Both genera have a narrow abdomen, but _Philoscia_ has an extra joint to the flagellum, and shows no sign of lateral lobes to the head. =Metoponorthus pruinosus= Brandt. PLATE XIX. 1833 _Porcellio pruinosus_ Brandt (3), p. 181. 1840 _Porcellio truncatus_ Milne-Edwards (46), p. 173. 1840 _Porcellio maculicornis_ Koch (34), part 34, pl. XVI. 1853 _Porcellio frontalis_ Lereboullet (39), p. 63, pl. I, fig. 17. 1868 _Porcellio pruinosus_ Bate and Westwood (1), p. 487. 1877 _Porcellio (Porcellioides) flavo-vittatus_ Miers (45), p. 669, pl., LXVIII., fig. 4. 1898 _Metoponorthus pruinosus_ Sars (59), p. 184, pl. LXXX., fig. 2. Undamaged specimens of _Metoponorthus pruinosus_ are of a beautiful bluish-grey colour, owing to a "bloom" which is easily brushed off, revealing a dark reddish-brown tint beneath it. The antennæ are long and have white markings upon them. Air-tubes occur in the first two abdominal appendages. [Illustration: FIG. 53.--FLAGELLUM AND LAST PEDUNCULAR JOINT OF THE ANTENNA OF _Metoponorthus pruinosus_.] _BRITISH LOCALITIES:--_ _England_: Maldon; (W.M.W. from R.M.): Hanwell; Eton Wick; Kew; Ipswich; Stoke-on-Trent; (W.M.W.): Chiselhurst; Oxford; (Bate and Westwood): Berkhamsted; Burnmoor; Durham; (Norman, 49): Exeter; (Parfitt, 53); Torquay; (B.M.--T.R.R.S.) _Scotland_: Banff; (Thomas Edwards in Norman, 49)