290 BULLETIN 152, UNITED STATES NATIONAL MUSEUM 



KEY TO THE AMERICAN SPECIES OF THE GENUS CYCLOXANTHOPS 



A'. Carapace nearly smooth, with a flattened marginal rim. Superior orbital 

 margin between fissures arcuate, not dentiform, surface flat. 



sexdecimdentatus, p. 290. 



A2. Carapace rugose, not rimmed. Superior orbital margin between fissures 



narrow, thick, raised. 



B'. Tooth at superior inner angle of orbit with a denticle on outer slope. 



Carapace narrow, a fringe of hair under lateral margin _vittatus, p. 291. 



B^. Tooth at superior inner angle of orbit without a denticle on outer slope. 



Carapace wider, margin naked noveiiadentatus, p. 292. 



CYCLOXANTHOPS SEXDECIMDENTATUS (Milne Edwards and Lucas) 



Plate 133, Figures 5 and 6; Plate 134, Figure 2; Plate 135, Figure 1 



Xantho sexdecimdentatus Milne Edwards and Lucas, d'Orbigny's Voy. Amer. 



Mer., vol. 6, pt. 1, 1844, p. 15; vol. 9, atlas, 1847, pi. 7, fig. 2 (type-locality, 



Chile; type in Paris Mus.). 

 Paraxanthus sexdecimdentatus Dana, U. S. Expl. Exped., vol. 13, Crust., part 1, 



1852, p. 172. 

 Cycloxanlhus sexdecemlineatus (by error) A. Milne Edwards, Crust. Reg. Mex., 



1879, p. 258. 

 Cycloxanthus sexdecemdentatus A. Milne Edwards, Crust. Re§. Mex., 1879, p. 



259. 

 C ycloxanthops sexdecimdentatus Rathbun, Proc. U. S. Nat. Mus., vol. 38, 1910. 



p. 541. 



Diagnosis. — Carapace nearly smooth and with a flattened marginal 

 rim. Superior orbital margin between fissures arcuate, surface 

 flat. A lobe below spine at inner angle of wrist. 



Description. — Carapace intermediate in width between the two 

 following species; convex except for a flat lateral rim which bears the 

 slightly upturned lateral teeth; surface nearly smooth. Regions 

 separated for the most part by broad shallow grooves; a large dimple 

 near middle of branchial region; a short obliciue ridge subparallel 

 to postlateral margin, and stopping abruptly inside the lateral rim. 

 First two lateral teeth subtruncate, remainder subacute, unequal; 

 last two teeth small and sometimes obscure. Front strongly ad- 

 vanced at middle, each lobe oblique, bilobed in smaller, nearly 

 straight in larger specimens. Major chela very heavy, the palm 

 increasing in width distally; fingers dark brown; a lobe below spine 

 at inner angle of wrist. 



Color. — Red tinged with yellowish above, bright fawn yellow 

 below; fingers and dactylus of ambulatory legs a bright brown 

 (Milne Edwards and Lucas). Carapace generally a dark prune 

 purple to claret brown, so dark that on higher parts of carapace it is 

 almost black; the same on antero-lateral spines. Chelae lavender, 

 lilac on upper margin, on prominent superior spine of carpus and on 

 smooth portions above. Teeth of fingers white, also tip of inner 

 carpal spine. The short curved groove on outer face of palm leading 

 down from articulation with dactylus is almost cadmium orange. 



