THE GRAPSOID CRABS OF AMERICA. 305 



SESARMA (HOLOMETOPUS) MAGDALENENSE, new species. 



Plate 86. 



Type-locality. Mangrove Island, Magdalena Bay, Lower Cali- 

 fornia; Mar. 20, 1911; Albatross; holotvpe male, Cat. No. 45793. 

 U.S.N.M. 



Diagnosis. Carapace broader than long, broadest anteriorly. Su- 

 perior frontal lobes low and nearly smooth. Front three-fifths as 

 wide as carapace. 



Description. Carapace distinctly broader than long, broadest at 

 outer angles of orbit, diminishing posteriorly, a very shallow sinus 

 in the lateral margins behind the antero-lateral angles. Surface for 

 the most part smooth and skining, depressions moderately deep ; pits 

 of two sorts, a few large scattered ones visible to the naked eye, and 

 numerous small ones, which become crowded on the anterior branch- 

 ial region. On the anterior and antero-lateral regions there are a 

 few scalelike granules. Antero-lateral angle a well-marked tooth. 



Front about three-fifths as wide as carapace, surface nearly ver- 

 tical, with the lower edge advanced; front widening below, lower 

 margin arcuate, outer corners rounded; surface uneven, wrinkled, 

 and unevenly granulate with fine, depressed granules; superior 

 frontal lobes nearly smooth and feebly separated, the middle pair the 

 wider. 



Chelipeds of male massive; merus and carpus covered on the outer 

 surface with short, granulated rugae; chelae high, swollen; immov- 

 able finger short, high, horizontal ; dactylus strongly arched. Palm 

 with lower margin very arcuate, its upper surface with several longi- 

 tudinal broken lines of fine granules, its outer surface, as well as the 

 upper surface of the proximal half of the dactylus, covered with fine 

 scabrous granules; fingers punctate, gaping: basal half of the pre- 

 hensile edge of the dactylus cut out in a deep sinus, into which pro- 

 jects a crenulated tooth of the immovable finger; both fingers irregu- 

 larly dentate. 



In the female both fingers are horizontal and longer than the im- 

 movable finger of the male; they do not gape and the teeth fit rather 

 closely together. The chelae of the young male are intermediate in 

 form between those of the female and of the adult male, and the gape 

 is lacking. 



Merus joints of legs rather short (in the fourth pair two and one- 

 fourth times as wide as long) , widening distally, and crossed by fine 

 short rugae: dactyli slender, longer than their respective propodi, 

 measured on the outer or anterior margin. 



Abdomen of male broadly triangular; terminal segment as broad 

 as long. Appendages of first segment rather slender, tips oblique. 



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