32 THE BKACHYUKA. 



The genus Ptychognathus already comprises 12 species and 1 subspecies, 

 all Indo-Pacific. Our species is most closely related to P. polleni de Man, 1 

 from Madagascar, in which the carapace is narrower and front wider, and 

 the branchial ridge arises near the last lateral tooth. 



Pseudograpsus albus Stimpson. 



Pseudograpsus albus Kingsley, Proc. Acad. Nat. Sci. Phil., 1880, 205. 

 Fakarava Island, Paumotus ; outer reef ; Oct. 12, 1899; 1 ? juv. 



Hemigrapsus elongatus (A. Milne Edwards). 

 PI. 2, Fig. 3; PI. 7, Figs. 2,2 a. 



Heterograpsus elongatus A. Milne Edwards, Nouv. Ai-ch. Mus. Hist. Nat. Paris, 1873, 

 9, 317, pi. 17, fig. 5. 



Tongabatu, shore; Nov. 22, 1899; 1 <?. 



The fronto-orbital width is a little less than the length, while the greatest 

 width of the carapace exceeds the length. Carapace almost smooth and 

 punctate, the punctae unequal in size and distribution. Posterior angles 

 of mesogastric region deeply marked. The postero-external surface of 

 the branchial region is very steep, and its upper margin is stronger 

 than the lower, and continued nearly to the posterior margin of the 

 carapace. Front very nearly half as wide as the carapace ; the lobes of 

 margin are separated by a broader sinus than shown in Milne Edwards's 

 figure. Upper margin of orbit sinuous, a notch at the inner end. Lateral 

 teeth blunt, formed by small triangular notches, the distance between them 

 less than the distance from the first to the orbital angle. 



The left cheliped only is present. Merus and carpus unarmed, the 

 inner angle of the latter bluntly rounded. Palm nearly as high as long, 

 and longer than the fingers, measured horizontally. The longitudinal 

 ridge on the lower half of the palm occupies only the proximal half. 

 Fingers strongly gaping. The large patch of thick hair on the inner 

 side of the chela extends half way on the palm and half way along the 

 pollex, and partly along the occludent edges of the fingers, even to the 

 outer side of the articulation of the dactylus. 



The ambulatory legs are chiefly light colored, with a few narrow bands 

 of the dark color of carapace and cheliped. They are sparsely furnished 

 with fine hairs. 



1 Op. cit., 1895, 9, 94 ; 1898, 10, pi. 28, fig. 20. 



