308 
Dr. Leach’s Arrangement of the Crustacea, <^c. 
and although from the infant state of our knowledge I cannot 
venture to propose named divisions, yet I shall endeavour to dis- 
pose the genera into what appear to be natural groups. 
A. Abdomen marts 5-articulaium articulo medio longiore, faemince 
7 -articulaium. Pedes 2 antici didactyli. 
Divisio I. Testa subrhomboidalis. Pedes duo aritici longissimi, di- 
gitis deflexis. 
Divisio II. Testa postiee truncata. Pedes duo antici maris elon- 
gati, foeminae mediocres. 
Suldivisio I. Antennae elongatae utrinque ciliatae. 
Testa elongato-ovata. Pedipalpi gemini externi articulo secundo 
longiore. 
Testa subcircularis ; orbita Integra. Ungues acuti, flexuosi. Pedi- 
palpi gemini externi caulis interni articulo secundo breviore. 
Testa subcircularis; orbita fissuris 2. Ungues recti. Pedipalpi 
gemini externi caulis interni articulo secundo longiore. 
Suldivisio 2. Antennae mediocres simplices. Pedes postici unguibus 
compressis, natatoriis. 
Orbita integra. Ungues omnes compressi. 
Orbita superne fissura 1. Ungues postici subcompressi, acuti. 
Orbita superne fissuris 2. Ungues postici valde compressi. Pedes 
2 antici inaequales. 
Orbita superne fissuris 2. Ungues postici valde compressi. Pedes 
2 antici aequales. 
Suldivisio 3. Antennae mediocres simplices. Pedes 8 postici natatorii. 
Suldivisio 4. Antennae simplices, breves. Pedes 8 postici consimiles, 
simplices. 
Pedes 2 antici simplices, inaequales. Antennae externae inter oculo- 10. Cancer. 
rum canthum et frontem insert*. 
Pedes 2 antici simplices, inaequales. Antennae in oculorura cantho 11. Xantho. 
interno insertae. 
Pedes 2 antici cristati, aequales. 12. Calapi'a. 
B. Abdomen in utroque sexu 7 -arlicidatum. Pedes duo antici di- 
dactyli. 
Genera. 
1. Lambrus. 
2. CORYSTES. 
3. Thia. 
4. Atelecyglus. 
5. PoRTUMNUS. 
6. Carcinus. 
7. PoRTUNUS. 
8. Lupa. 
9. Matuta. 
Divisio 
