South African Crustacea. 85 



measured round the back was 44 mm., the carapace being 13'5 mm., 

 the telson 6 mm. long. 



Locality. 33 50' S., 25 46' E. ; depth 20 fathoms. A 1561. 



GEN. SYNALPHEUS, Bate. 



1888. Synalpheus, Bate, Eep. Voy. Challenger, vol. 24, pp. 480, 572. 



1899. ,, Coutiere, Ann. Sci. Nat. Zool., Ser. 8, vol. 9, 



pp. 154, 334, etc. 



1905. ,, Coutiere, Fauna Maldive-Laccadive Archip., 



vol. 2, pt. 4, pp. 853, 869. 



1909. Coutiere, Pr. U.S. Mus., vol. 36, pp. 1-93. 



1911. ,, de Man, Siboga Exp., vol. 39a, p. 185. 



1913. Zimmer, Zool. Jahrb., Suppl. 11, pt. 3, p. 381. 



In Bate's original definition of the genus a salient point is 

 the statement that the mandibles have a curved, sharply 

 pointed, and almost rudimentary incisor process, with a 

 small two-jointed palp. But Professor Coutiere in 1899 

 explains that, while this is true for the single species on which 

 Bate founded his genus, there are gradations which lead 

 through closely allied species from this form of mandible 

 to that which may be regarded as normal in this genus and 

 Alpheus. Authors may well be excused for not foreseeing 

 discoveries of this kind, since in the process of evolution every 

 peculiarity, however striking, is liable to be neutralized in the 

 same way for purposes of classification. A new and full 

 description of the generic character is given by Coutiere in 

 1899. As often happens, some of the features are shared with 

 neighbouring genera, and some of the distinguishing points, 

 besides the incisor of the mandibles, are alternative. Since 

 1888 there has been an amazing development of the genus, 

 for in place of the single species then assigned to it by Bate, 

 de Man in 1911 enumerated 62 species and 15 varieties from 

 the Indo-Pacific region alone. In the discrimination of these 

 species minute measurement plays an almost alarming part, 

 because as the eyes are completely covered by the carapace 

 the vision of these creatures must be dim, and without com- 

 passes the members of different species will never know one 

 another apart. Perhaps indeed the numerous varieties may 

 be the result of inconsiderate intermarriages. 



In 1909 Coutiere distributed the species then known among 

 six groups, with keys which must be invaluable to those who 



