CARCINOI.OGICAL STUDIES. '27 



rax have a different direction; they form a regularly- 

 undulate, S-1 i k e line in the species of de Haan , 

 different from what is seen in Gelas. Dussumieri. 



The two longitudinal grooves by which the gastric and 

 cardiac regions are separated from the branchial regions , 

 are deep in the male of Gelas. Dussumieri, but rather 

 shallow in the other species. The external orbital angles 

 are much more acute and directed more obliquely outward 

 than those of Gelas. arcuatus. 



The larger hand of the male has a different form in 

 both species. The lower finger of Gelas. Dussumieri is 

 constantly armed with only one single prominent 

 tooth a little before the middle, but for the rest 

 it is unarmed and terminates in an acute point, slightly 

 curved upward. The dactylus or mobile finger presents 

 only some more or less prominent granules along its pro- 

 ximal half. The lower finger of Gelas. arcuatus, on the 

 contrary, presents always two teeth, one a little before or 

 in the middle, the other near the extremity, and more or 

 less prominent granules are observed in this species along 

 the whole length of the inner margin of the dactylus. 



The ambulatory legs, finally, are a little less slender 

 in Gelas. arcuatus , the meropodites being slightly more 

 enlarged. 



I give the measurements of some specimens: 



Millim. 

 1. 

 Distance between the ext. orb. angles 87^/3 

 Length of the cephalothorax (front 



included) 22 V4 



Length of the larger hand ... 72 



» » » palm of ditto . . .18 



N°. 1, adult male from Java; N°. 2, male from Ponape ; 

 N°. 3, young male from Amboina without, and N°. 4, young 

 male from Amboina provided with a trace of an accessory 

 row of granules near the inferior margin of the orbits. 



N'otes from the Leyden. ÜMuseum , Vol. ^XIIII. 



