122 GAMMA RID^E. 



are longer than the preceding, and more slender, and 

 have the third joints and the wrists not broader than 

 the next succeeding joints. 



The segment of the body which carries the ante- 

 penultimate pair of caudal appendages is remarkable 

 for a notch, deeply cut, near the middle, into its dorsal 

 surface. The appendages are shorter than the penulti- 

 mate ; the penultimate is shorter than the ultimate ; and 

 both have their branches equal. The last pair have but 

 one branch, which is much longer than the peduncle, and 

 tipped with a strong single spine. The terminal plate is 

 double, as in the genus Gammarus, each division being 

 subapically tipped with a single spinule. 



The colour of the animal, when taken alive, is of a 

 tolerably bright lemon, every segment and joint being 

 fringed with a margin of white; the whole animal is 

 thickly covered with minute black spots. The speci- 

 mens which have been sent to us, being dead, were 

 generally fawn-coloured, tending to a bluish-grey upon 

 the back. This constant appearance, together with the 

 animal being less compressed than Anonyx and Lysia- 

 nassa, enabled us readily to recognize any specimen. 



The first species of this genus was indicated by the 

 elder Costa in his " Catalogue of Nepalese Crustacea," 

 published in 1840, and was subsequently described and 

 figured in the " Fauna del Regno di Napoli, Crust.," pi. 8, 

 fig. 47, by his son. The lower antennae are not longer 

 than the upper. A second species, C. Hopei, also from 

 the Bay of Naples, was described and figured by the 

 latter author in the " Catalogo dei Crostacei Italiani," 

 published by the Rev. F. W. Hope, Naples, 1851 ; and 

 in the "Fauna del Regno di Napoli," pi. viii. fig. 1. 

 The lower antennae in this species are more than half the 

 entire length of the animal. 



