284 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxii. 



POTAMON (POTAMONAUTES) DUBIUS (Capello) . 



Thelphusa duhia Capello, Jor. Sci. LisLoa, IV, 1873, p. 254, pi. i, figs, la, 2a. — A. 



Milne-Edwards, Ann. Sci. Nat., Zool. (7), IV, 1887, p. 129. 

 Potamon (Potamonautes) duhium Ortmann, Zool. Jahrb., Syst., X, 1897, p. 307. 



African localities. — St. Thomas (Osorio); Kunene Eiver, Mossamedes 

 (Capello); Angola, Humbe, and Kunene Eiver (Osorio)^ Kazungula, 

 Zambesi (U.S.N.M.). 



POTAMON (POTAMONAUTES) BAYONIANUS (Capello). 



Thelphusa bai/oniana Capello, Desc. tres esp. nov. Crust. Afr. occ, Lisboa, 1864, 

 p. 2, pi. I, fig. 3; Mem. Acad. B. Sci. Lisboa, CI. Sci., Nova Ser., II, 1865, Pt.2; 

 Jor. Sci. Lisboa, III, 1870, p. 131, pi. 2a, fig. 10. — A. Milne-Edwards, Ann. 

 Sci. Nat., Zool. (7), IV, 1887, p. 128. 



Potamon (Potamonautes) hayonianum Ortmann, Zool. Jabrb., Syst., X, 1897, p. 306. 



African localities. — Angola: To the north of Quibula; Duque de 

 Braganca; Kakonda; Huilla; Kunene River (Osorio). 



POTAMON (POTAMONAUTES) BALLAYI (A. Milne-Edwards). 



Thelphusa ballayi A. Milne-Edwards, Bull. Soc. Philom. (7), X, 1886, p. 149; 

 Ann. Sci. Nat., Zool. (7), IV, 1887, p. 132, figs. 2, 2a, 2b. 



African locality. — Nganciu on the Kongo (A. Milne-Edwards). 



POTAMON (POTAMONAUTES) PERLATUS (Milne-Edwards). 



Thelphusa perlata Milne-Edwards, Hist. Nat. Crust., II, 1837, p. 13. 

 Potamon {Potamonautes) perlatum Ortmann (part), Zool. Jabrb., Syst., X, 1897, 

 p. 307. 



African localities. — Zanzibar and Zanzibar coast (Pfeffer); Natal 

 (Krauss, Ortmann); Cape Colony (Milne-Edwards, Krauss, Heller); 

 Constantia (Stimpson); Cape Town (Miers); Wellington (Miers); Chalk 

 Bay (Studer); Biballa and Caconda (Osorio); 400 miles inland from 

 Loanda in River Cuiji — H. Chatelain, collector (U.S.N.M.). "Found in 

 ponds and swamps; eaten by the natives; called ' Hala.'" 



Subgenus GEOTHELPHUSA Stimpson. 



POTAMON (GEOTHELPHUSA) MACROPUS Rathbun. 



Potamon {Geothelphusa) macropus Eathbtjn, Proc. Biol. Soc. Washington, XII, 

 1898, p. 29, pi. II, figs. 1-4. 



African locality. — Mouth of Mesurado River, Monrovia; O. F. Cook, 

 collector. ' 



Genus PARATHELPHUSA Milne-Edwards. 



KEY TO THE WEST AFRICAN SPECIES OF THE GENUS PARATHELPHUSA. 



A. Lateral margin with only one tooth behind the post-frontal crest chavanesi. 



A'. Lateral margin with more than one tooth behind the jiost-frontal crest. 

 B. Lateral margin with more than three teeth behind the post-frontal crest. 



C. Carapace narrow ; post-frontal crest feeble hrazzoe. 



C . Carapace broad ; post-frontal crest distinct chaperi. 



B'. Lateral margin with only three teeth behind the post-frontal crest. 



C. Post- frontal crest uninterrupted, nearly straight pwcilei. 



C Post-frontal crest arcuate, uneven, interrupted campi. 



