3 o8 



Brevirostris group. 



Lateral (extra-corneal) spines wanting. Larger chela quadrangular, compressed, often with 

 longitudinal ridges, with a transverse groove near the articulation of the dactylus or not ; 

 dactylus of larger chela of the male sometimes "Balaeniceps"-shaped. Merus of third legs 

 usually unarmed. Dactyli of three posterior legs simple, lanceolate. 



Edivardsi group. 



Lateral (extra-corneal) spines wanting, very rarely (A. hoplites) orbital hoods acute. 

 Larger chela usually more or less compressed, with both the upper and the lower margin 

 emarginate and with grooves or depressions on the lateral surfaces. Dactylus of smaller chela 

 of the male often "Balaeniceps"-shaped, rarely also that of the female. Merus of third legs 

 unarmed or dentate. Dactyli of three posterior legs simple, very rarely [A. hoplites, A. Polyxó) 

 biunguiculate. 



Key to the indopacific species and varieties of the genus Alphens Fabr 



Megacheles group. 



a x Merus of 3 rd legs unarmed. 



ó } Dactylus of 3 rd and following legs simple. 



c x Merus of 3 rd legs 5-times longer than wide. Fingers of the smaller 

 chela slightly shorter than the palm, which is 2,43-times as long 



as high stapliylimis Cout. 



(H. COUTIÈRE, in: Buil. Soc. Philom. Paris, 1908, p. 14). 



c„ Merus of 3 rd legs 9, 5-times longer than wide. Inner margin of 

 the merus of the larger cheliped with 4 — 6 small spinules 

 posterior to the spine at distal extremity. Fourth article of carpus 

 of 2 nd legs usually as long as the 2 nd and as long as the 5 111 . 

 Fingers of the smaller chela slightly longer than the palm. 

 Larger chela in the male 2,58-times, in the female 2,76-times 

 as long- as hio-h Hailstonei Cout. var. assimulaus de Man 



£ 3 Merus of 3 rd legs 11-times longer than wide 1 ). Inner margin of 

 the merus of the larger cheliped unarmed posterior to the spine 

 at distal extremity. Fourth article of carpus of 2 nd legs as long 

 as the 2 nd and as long as the 5 th . Fingers of smaller chela 

 slightly shorter than the palm. Larger chela 3,33-times as long 



as high Hailstouci Cout. 



(H. COUTIÈRE, Alpheidae Mald. and Laccad. Archip. 1905, p. 879, PI. LXXIV, fig. 18). 



1) This proportion is deduced fiom the figure. 



176 



