8. Uropods with two slender branches extending well posterior to the body 



and with the inner branch a little longer than the outer branch; Family 

 Ligiidae 



Ligidium Brandt 

 Uropods not so — either extending scarcely behind the body or with the 

 outer branch a little longer than the inner branch 9. 



9. Uropods not extending backwards beyond the rear projections of the last 



segment of the abdomen; animal can roll itself into a ball 10. 



Uropods extending a little behind the rear projections of the last seg' 



ment of the abdomen; most species (but not all) cannot roll into a 



ball 11. 



10. Front margin of head indented in the middle; generally distributed; 



Family ArmadiUidudae 



Armadillidium Brandt 

 Front margin of head straight; California; Family Cuharidae 

 Cuharis Brandt 



11. Largest of antennal segments about one-half the length of the divisions 



of the thorax; mouth parts forming a very conspicuous mass; Family 



Trichoniscidae 12. 



Largest of antennal segments about as long as or longer than the divisions 



of the thorax; mouth parts not prominent 13. 



12. Abdomen about the same width as the thorax 



Haplophthahnus Schobel 

 Abdomen abruptly narrower than the thorax 

 Trichoniscus Brandt 



13. Abdomen abruptly narrower than the thorax; Family Oniscidae (part) 



14. 

 Abdomen not abruptly narrower than the thorax 15. 



14. With three sections in antennal flagellum 



Philoscia Latreille 

 With two sections in antennal flagellum 

 Porcellionides Miers 

 (Metoponorthus Buddc-lund) 



15. With two sections in antennal flagellum; Family Oniscidae (part) 16. 

 With three or four sections in antennal flagellum 18. 



16. Body very convex; can roll into a ball 



Cyhsticus Schnitzler 

 Body moderately convex; cannot roll into a ball 17. 



17. With white respiratory sacs on five pairs of pleopods 



Tracheoniscus Verhoeif 

 (Trachehpus Budde-Lund) 

 With white respiratory sacs on two pairs of pleopods 

 Porcellw Latreille 



18. Posterior margin of last abdominal segment produced backwards in the 



middle to form a projection between the uropods 

 Omscus Linn, (of Family Oniscidae) 

 Posterior margin of last abdominal segment regularly curved 19. 



190 



