_Porcellio dilatatus_ Brandt 33 _Porcellio rathkei_ Brandt 34 _Porcellio laevis_ Latreille 35 _Porcellio ratzeburgii_ Brandt 36 Genus--Metoponorthus Budde-Lund 37 _Metoponorthus pruinosus_ Brandt 37 _Metoponorthus cingendus_ Kinahan 38 Genus--Cylisticus Schnitzler 38 _Cylisticus convexus_ De Geer 39 Family--Armadillidiidæ 40 Genus--Armadillidium Brandt 40 _Armadillidium nasatum_ Budde-Lund 40 _Armadillidium vulgare_ Latreille 41 _Armadillidium pulchellum_ Zencker 42 _Armadillidium depressum_ Brandt 43 Distribution of species 43 Conclusion 43 Bibliography 49 LIST OF FIGURES. PLATES I.-XXV. with a List, will be found at the end of the Book. FIGURE. PAGE. 1. Parts of the body (_Oniscus asellus_) 2 2. The first antenna (_Oniscus asellus_) 2 3. The second antenna (_Oniscus asellus_) 3 4. The underside of the head (_Oniscus asellus_) 3 5. The mandibles (_Oniscus asellus_) 4 6. The first maxillae (_Oniscus asellus_) 4 7. The second maxillae (_Oniscus asellus_) 4 8. The fused maxillipeds (_Oniscus asellus_) 4 9. The "upper lip" (_Oniscus asellus_) 5 10. The "lower lip" (_Oniscus asellus_) 5 11. A typical thoracic segment (_Oniscus asellus_) 5 12. The fifth thoracic segment of a female (_Oniscus asellus_) 5 13. The underside of the abdomen of a female (_Oniscus asellus_) 6 14. A typical abdominal appendage (_Oniscus asellus_) 6 15. The first abdominal appendage of the male (_Oniscus asellus_) 6 16. The second abdominal appendage of the male (_Oniscus asellus_) 6 17. The alimentary canal (_Oniscus asellus_) 7 18. The circulatory system (_Oniscus asellus_) 7 19. The nervous system (_Oniscus asellus_) 8 20.