Length of carpo- and propodite together | 

 Length of propodite in the median line | 



Breadth of propodite 

 Length of dactylus 



74 



of penultimate pair of legs 



In typical Grapsus strigosus and in Grapsus longitarsis the length of the carapace 

 exceeds the distance between the outer orbital angles, but in the smaller "Siboga"-specimen 

 the reverse is the case, ovving to the carapace being scarcely narrowed anteriorly. 



Geograpsus Stimpson. 



1858. Geograpsus Stimpson. Proc. Ac. Nat. Sc. Philadelphia, 1858, p. 101. 



The genus is distinguished from Grapsus by straight or nearly straight lateral margins 

 of the carapace, by a much less defined epistome, and by more bulky chelipeds, the fingers ot 

 which are not spoon-shaped but acute at the tip. 



The habits of the members of Geograpsus are almost like those of the true landcrabs 

 (Gecarcinidae). 



Thanks to de Man's researches, it is now easy to discriminate the Indo-Pacific species 

 by means of the following key : ) : 



1 . Lateral margins of carapace distinctly converging backward 



behind epibranchial teeth, Rnd obtuse, not keeled in their 

 posterior half. Inferior orbital border, between external 



angle and fissure, entire, not dentate G.grayi (H.Milne-Edwards) 3 ) 



Lateral margins of carapace parallel or feebly diverging back- 

 ward, sharply keeled throughout 2 



2. Cardiac and intestinal regions of carapace nearly wholly smooth, 



with only a few transverse lines immediately behind cervical 



groove. Breadth of meropodites of last pair of legs more 



than half their length ; posterior margin of preceding ambul- 



atory legs distinctly dentate at distal extremity ... . . G. lividus (H. Milne-Edwards) 



subsp. stormi de Man 

 Cardiac and intestinal regions of carapace covered with irregular 



transverse lines ; grooves on branchial regions deeply cut and 



long. Breadth of meropodites of last pair of legs not more than 



half their length; posterior margin of preceding ambulatory 



legs not at all, or very indistinctly, dentate at distal extremity G. crinipes Dana 3 ) 



1) I have not been able of including one species into this key, Geograpsus minikoiensis Borradaile (Faun. Geogr. Maldives etc, 

 v. 1. 190I1 p. 66, f. 12 and Transact. Linn. Soc. London (2) v. 12, 1907, p. 64 from Minikoi and the Seychelles; this species is much 

 too little known. 



2) Literature and description : ue Man, Zool. Jahrb., Syst., Bd 9, 1895, p. 80 and Ai.cock, Journ. As. Soc. Bengal, v. 69, 

 prt 2, 1900. p. 395. Throughout Indo-Pacific region. 



3) Literature and description: de Man, Zool. Jahrb., Syst., Bd 9, 1895, p. 83, Bd 10, 1898, pi. 28, f. 17. Alcock's description 



eems to be applied equally well to G. crinipes as to G. lividus subsp. stormt^ for the transverse markings on the carapace 



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