78 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 5 



Chelipeds of male grossly disproportionate, smooth, naked, faintly 

 reticulate. Merus of larger cheliped heavy, breadth almost equal to 

 length, a superior row of granules culminating in a near-tubercle, and 

 a deep subdistal indentation. Carpus lumpy, a reticulate pattern exteri- 

 orly, a blunt tooth at inner angle. Chela gargantuan, approaching half 

 of carapace displacement; palm tumid, nearly as high as wide, inferior 

 border sinuous; dactyl fully as long as superior length of manus, color 

 not covering basal fourth, tip deflexed; fingers meeting with a gape one 

 third as high as wide, teeth white tipped, the larger separated by a denti- 

 cle, well worn in the male specimen. (See pi. 20, fig. 3.) Minor cheliped 

 a fraction of the size of major, carpus more uneven, manus strongly re- 

 ticulate, fingers channeled, granulate, meeting without gape, pollex de- 

 flexed. (See pi. 20, fig. 4.) 



Ambulatory legs moderately slender; merus granulate, especially 

 above ; carpus grooved and broadening distally ; propodus, particularly of 

 last leg, wide; dactylus long, straight, and pilose; margins of all seg- 

 ments hairy. 



Female similar to male except for more nearly proportionate cheli- 

 peds. Major chela like minor chela of male except for the more promi- 

 nent triangular cutting teeth and upturned tip of pollex, crossing dactyl. 

 (See pi. 20, fig. 5.) Minor chela of both sexes alike. 



Color in life: Carapace and cheliped dull yellow densely speckled 

 with white and hellebore red. Ambulatory legs, including dactyl, yellow 

 touched on upper surface with neutral red. Ventral surface also yellow, 

 densely spotted on abdomen and sternum with red and scattered spots 

 elsewhere. (Petersen) 



Remarks: The discoveiy of a Platyxanthus in Panamanian waters 

 extends the range of this South American genus into the Northern Hemi- 

 sphere. The writer is indebted to Mr. Steve A. Glassell for a clue to the 

 affinities of the new species, which differs so remarkably from its con- 

 geners in appearance that structural similarities are obscured. These are 

 typically xanthid in form, being from one third to one half broader than 

 long, having the front but little advanced beyond the anterolateral arch, 

 which is dentate rather than tuberculate. While five lateral teeth are the 

 rule in the genus (although any or all may be subdivided), the exorbital 

 in balboai is so small and far removed that it is for all practical purposes 

 a four-toothed species. Of the known Pacific Platyxanthus it is perhaps 

 nearest P. cokeri Rathbun (1930) and most distant from P. orbignyi 

 (Milne Edwards and Lucas) (1843), a specimen of which at hand 



