34 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 60 



15. Dorsal plate invaginate posteriorly ; third legs of the usual pattern ; fifth 

 legs present 3.15 mm., female, ratMuni, new species, p. 39 



15. Dorsal plate evenly rounded posteriorly; third legs enlarged at their tips; 

 no fifth legs 2.50 mm., female, leidyi, new species, p. 40 



16. Tips of anal laminae almost or quite reaching posterior margin of dorsal 

 plate; fourth legs projecting nearly their entire length 17 



16. Tips of anal laminae considerably in front of posterior margin of dorsal 

 plate; fourth legs projecting half their length or less 18 



17. First antennae rudimentary ; cephalothorax much narrower than free 

 thorax: third legs parallel female, hrevls Richiardi, 1886 



17. First antennae three-jointed; cephalothorax as wide as free thorax and 

 notched on either side 5 mm., female, nobilis Hell6r, 1865 



17. First antennae five-jointed ; cephalothorax much narrower than free thorax ; 

 third legs divergent 5 mm., female, gisleri P. J. van Beneden, 1852 



17. First antennae eight- jointed ; cephalothorax much narrower than free 

 thorax ; third legs parallel — 7 mm., female, powatomi R. Rathbun, 1887, p. 42 



18. First antennae rudimentary ; cephalothorax much narrowed anteriorly ; 

 third legs parallel; fourth legs narrow, acuminate laminae, with the tips 

 only projecting 4 mm., female, Icoenigii Steenstrup and Liitken, 1861 



18. First antennae three-jointed; cephalothorax slightly narrowed anteriorly; 

 third legs parallel ; fourth legs broad laminae, bluntly rounded, projecting 

 their whole length 5 mm., female, brevoortiae R. Rathbun, 1887, p. 43 



18. First antennae rudimentary ; cephalothorax with a horn-like process at 

 each anterior corner; third legs parallel; fourth legs with acuminate 

 laminae 4.75 mm., female, spictdatus Wilson, 1913 



18. First antennae prominent, six-jointed; cephalothorax widened anteriorly; 



third legs widely divergent; fourth legs narrow blunt laminae, not pro- 

 jecting at all 8 mm., female, trifoliatus Bassett-Sraith, 1898 



19. Dorsal plate not covering fourth legs; no posterior sinus; body only twice 

 as long as wide or less 20 



19. Dorsal plate covering fourth legs and wrapped around ventrally like the 

 skirts of a cloak 23 



20. Rami of fourth legs slender, cylindrical, and acuminate; anal laminae only 

 reaching the center of the dorsal plate 21 



20. Rami of fourth legs broad laminae; anal laminae almost or quite reaching 

 the posterior margin of the dorsal plate 22 



21. Cephalothorax with a long conical process projecting laterally from each 

 posterior corner 7 mm. female, tylosuri Richiardi, 1880 



21. Cephalothorax ovate with smoothly rounded margins; no processes; free 

 thorax wider than long 2.25 mm., female, pagodus Kr^yer, 1863 



22. Rami of fourth legs projecting nearly their entire length, with filiform 

 tips 5.50 ram., female, foliaceiis Richiardi, 1880 



22. Rami of fourth legs projecting only half their length ; bluntly pointed, not 

 divided to their base 5 mm., female, krpyeri Beneden, 18-51 



22. Rami of fourth legs projecting only half their length ; bluntly rounded, 

 armed with spiny processes 6 mm., female, lappaceus Wilson, 1912 



23. Dorsal plate in dorsal view shaped like an hourglass ; cephalothorax one- 

 third the entire length 3 mm., female, chlamydotus, new species, p. 48 



23. Dorsal plate with straight lateral margins; cephalothorax only one-sixth 

 the entire length 9.50 mm., female, paenulatus, new species, p. 51 



24. Dorsal plate entirely covering the fourth legs; third legs broad laminae 

 with bluntly rounded tips 25 



24. Fourth legs projecting more or less; third legs narrower laminae vvith 

 pointed tips; fifth legs present 26 



