134 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



8 — Legs all of same size Genus Pcdicnlus 



Anterior legs much smaller than others. , .Genus Phthirns 



9 — Antennae five-segmented ! 11 



Antennre three-segmented. Subfamily Euh.ematopi- 

 NiN^: 10 



10 — Posterior legs with stalked, disk-shaped appendages on 



femur and tibia Genus Euhccmatopimis 



Posterior legs without such appendages 



Genus Hceuiatopinoides 



11 — Legs and claws all practically of equal size 



Subfamily TLTiMATOPiNiNTE Genus Hcematopinus 



Anterior legs smaller and with slenderer claw than 

 the posterior pair, at least. Subfamily Linognathin^..12 



12 — Anterior tarsi with two joints Genus Hyhophthirns 



Anterior tarsi with but one joint 13 



13 — Anterior tarsi with a short, claw-like process in addi- 

 tion to the claw Genus Scipio 



Anterior tarsi not so 14 



14 — Abdomen with well developed pleural plates 18 



Abdomen entirely without pleural plates 15 



15 — Abdomen with more than one row of hairs or spines 



on each segment Genus Linognathiis 



Abdomen with but one row of hairs on each segment. . 16 



16 — Gonapods moderately long, behind each gonapod a 



stout, flat, spine-like process Genus Cervophthirius 



Gonapods very short, no flat, spine-like process behind 

 them Genus Hcumodipsiis (in part) 



18 — Anterior pair of legs equal to middle pair, both pairs 



very small, posterior pair large and stout 



Genus Enderleinellns 



Anterior legs smaller than either middle and poste- 

 rior legs and with much smaller and more slender claw. 19 



19 — Second or third abdominal sternite with a chitinized 

 plate or area near each lateral margin . Genus Fahrenholsia 



Second or third abdominal sternite without such 

 plates 20 



20 — Abdominal segments with but a single transverse row 



of spines 21 



Abdominal segments, at least in part, with two or 

 more transverse rows of spines 22 



