174 STALK-EVED CRUSTACEA 



ridged ; the ridges may terminate in spines ; the palm is 

 elongated and somewhat prismatic ; the fingers, straight, 

 incurved at the apices, are armed with numerous unequal 

 lobes or tubercles on the inner margins. The walking legs 

 are considerably elongated, with the two last joints com- 

 pressed and longitudinally sulcated ; in the last pair these 

 joints are usually smooth, dilated, and the last joint oval 

 and flat. 



Range. — Warm and temperate seas in shallow and 

 deep water; also in the gulf weed on the surface of the sea. 



Subgenus I. Neptunus. 



Subgenus II. Amphitrite. 



Subgenus III. Achelous. 



Subgenus IV. Hellenus. 



Synopsis of the Subgenera and Species. 



A. Spine on the interior margin of the fifth joint of 

 the first pair of legs normally developed. 



(7. Lateral epibranchial spine much longer than the 

 preceding tooth of antero-lateral border. 



a'^. Carapace broadly transverse ; antero-lateral margins 

 forming with the frontal margin a regular curve with a 

 long radius. — (Subgenus A'r/fufius.) 



1. The fourth joint of the first pair of legs has four 

 spines in front, no spine behind. — (iV. saj'i.) 



2. The fourth joint of the first pair of legs has three 

 spines in front, one spine behind. — (iV. cribrarius^ 



b^. Carapace narrower ; antero-lateral margins forming 

 with the frontal margin a curve with short radius, or an 

 angle. — (Subgenus A mphitrite?) 



3. The fourth joint of the first pair of legs has four 

 small curved spines in front ; one spine at external angle 

 The sternal plastron is smooth. — (A^. ojiccps.) 



