STALK-EYED CRUSTACEA 175 



4. The fourth joint of the first pair of legs has two 

 spines, and some spinules on anterior border ; a short 

 flat spine at extremity of posterior border. Sternal 

 plastron with grooves. Carapace more or less smooth. 

 — (A^. ventralis.) 



5. Carapace with deep grooves. Sternal plastron 

 smooth. — {N. stilcatus.) 



6. Carapace almost hexagonal. A round red spot on 

 each side of posterior portion. — (A^. scbce?) 



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

 spines in front, one behind. The external plastron is 

 rough. — {N. ordivayi.) 



b. Lateral epibranchial spine no longer or very little 

 longer than the preceding tooth of the antero-lateral 

 border. — (Subgenus Achelous.) 



8. The front is cut into eight teeth ; the internal orbital 

 angle bifid. — ( N. spinij)ianus.) 



9. The front is cut into six teeth. — (A^. depress if fotis.) 

 B. Spine on inner margin of fifth joint of first pair of 



legs abnormally developed ; in adult male longer than the 

 palm. — (Subgenus Helietius.) 



10. Spine on carpus reaches the anterior third of hand. 

 Middle teeth of front the longest. — (A^. spinicarptis.) 



Subgenus Neptunus. 



Neptiinus Miers. 



Neptunes argues ... A. Milne Edwards. 



Carapace broadly transverse ; antero-lateral margins 

 forming with the frontal margin a regular curve with a 

 long radius. Lateral epibranchial spine much longer than 

 the preceding teeth of the antero-lateral border. The 

 spine on the inner margin of the fifth joint of the first pair 

 of legs normally developed. 



