THE CANCROID CRABS OF AMERICA 139 



interorbital space wide; antero-lateral teeth very unequal, alternating 

 large and small; chelipeds heavy. 

 Contains only two species. 



KEY TO THE SPECIES OF THE GENUS CRONIUS 



A'. Four spines on manus. A spine at postero-distal angle of merus of swimming 

 feet . ruber, p. 139. 



A'. Two spines on manus. A row of spinules but no spine on postero-distal 

 margin of merus of swimming feet tumidulus, p. 142. 



CRONIUS RUBER (Lamarck) 



Plates 62 and 63 



Portunus ruber Lamarck, Hist. Nat. Anim. sans Vert., vol. 5, 1818, p. 260 (type- 

 locality, Brazil; type not located). 

 Lupa rubra Milne Edwards, Hist. Nat. Crust., vol. 1, 1834, p. 454.— Streets, 



Proc. Acad. Nat. Sci. Philadelphia, ser. 3, vol. 1, 1871, p. 239; Isthmus of 



Panama. 

 Cronius ruber Stimpson, Ann. Lye. Nat. Hist. New York, vol. 7, 1860, p. 225 [97]. 

 Achelous ruber A. Milne Edwards, Arch. Mus. Hist. Nat., Paris, vol. 10, 1861, 



p. 345, pi. 33, fig. 1-16. 

 Goniosoma millerii A. Milne Edwards, Nouv. Arch. Mus. Hist. Nat., Paris, vol. 4, 



1869, p. 54, pi. 18, figs. 1-3 (type-locality. Cape St. Vincent, Cape Verde 



Islands; type in Paris Mus.). 

 Am-phitrite edwardsii Lockington, Proc. California Acad. Sci., vol 7, 1876 (1877), 



p. 43 [3] (type-locality, Mazatlan; type not extant); p. 106 [12], Lower 



California. 

 Cronius milleri A. Milne Edwards, Crust. Reg. Mex., 1879, p. 232. 

 Cronius edwardsii A. Milne Edwards, Crust. Reg. Mex., 1879, p. 232. 

 ChanjbdeUa rubra Rathbun, Proc. U. S. Nat. Mus., vol. 22, 1900, p. 291. 

 Charybdella edwardsii Rathbtjn, Proc. U. S. Nat. Mus., vol. 38, 1910, p. 611. 



Diagnosis. — ^Two gastric, one branchial ridge. Upper inner orb tal 

 angle distinctly divided into two teeth. All spines black-tipped. 

 Four spines on v/rist, 4 on hand. A strong spine at postero-distal 

 angle of merus of swimming foot. 



Description. — Carapace hexagonal, smooth and pubescent. A sin- 

 uous branchial ridge, two gastric ridges, the anterior one bi-arcuate. 

 Front proper cut into four teeth, the two median more advanced, 

 larger, and with convex sides; those of second pair more pointed, 

 directed slightly outward and separated from the antennal tooth by a 

 deep cut; this pair narrow, sharp, directed forward, and not deeply 

 separated from the inner orbital angles and are subrectangular and 

 carinate. Orbit nearly circular. The basal article of the external 

 antennae bears a spine below the insertion of the movable portion. Of 

 the antero-lateral teeth or spines the ninth is scarcely longer than the 

 seventh; intermediate spines strikingly smaller. Merus of chelipeds 

 armed in front with from four to six spines of unequal size, one of 

 which is terminal, and at extremity of its posterior border with a very 

 small spine. Wrist with granulous crests, a large spine inside and 



