236 Annals of the South African Museum. 



FAMILY PORTUNIDAE. 

 GEN. ACHELOUS, de Haan. 



1833. Achelous (subgen. of Portunus), de Haan, Crustacea Japonica, 



decas 1, p. 8. 

 1899. (subgen. of Neptunus}, Alcoclc, J. Asiat. Soc. Bengal* 



vol. 68, pt. 2, pp. 9, 30. 

 1901- (subgen. of Portunus}, Eathbun, U.S. Fish. Comm. 



Bull., 1900, vol. 2, p. 44. 



1906. Rathbun, U.S. Fish Comm. 



Bull., 1903, pt. 3, p. 371. 



1910. Stebbing, Aim. S.A. Mus., vol. 6, pt. 4, p. 307. 



In defining this genus or subgenus de Haan states that of the 

 nine teeth of the autero-lateral margin the hindmost tooth is 

 scarcely longer than the preceding teeth. In the species now to 

 be mentioned it has been observed that the tooth in question is 

 actually smaller than those which precede it. 



ACHELOUS ORBICULARIS, Richters. 



1880. Achelous orbicularis, Richters, in Mobius, Meeresf. Maurit., 



p. 153, pi. 16, figs. 14, 15. 

 1893. ,, Henderson, Tr. Linn. Soc. London, ser. 2, 



vol. 5, pt. 10, p. 371. 

 1899. Neptunus (Achelous} orbicularis, Alcock, J. Asiat. Soc. Bengal, 



vol. 68, pt. 2, p. 47. 



1906. Portunus (Achelous) orbicularis, Rathbun, U.S. Fish. Comm., 



p. 871, pi. 12, fig. 4. 



1911. ,, ,, ,, Rathbun, Tr. Linn. Soc. 



London, ser. 2, vol. 14, 

 pt. 2, p. 206. 



The specimen measures 24 mm. at the broadest part, between 

 the apices of the seventh antero-lateral denticles, with a median 

 length of 18 mm., the length being thus six-eighths of the breadth, 

 as compared with six-sevenths recorded by Alcock. The sub- 

 circular appearance, however, is increased by a slight protrusion 

 of the third maxillipeds in front, and of the pleon to the rear. 

 The telson of the female is triangular, ending bluntly, abruptly 

 narrower than the preceding segment. The first two segments 

 of the pleou are extremely short, not clearly separated. The 

 third segment is the widest of all, sharply ridged, not very long ; 

 the fourth is also short, exceeded in breadth by the fifth, which, 



