Mr. A. O. Walker on Pherusa fucicola (Leach). 421 



rella brevicaudata ¥ to the smallest detail. The solitary- 

 species therefore on which Leach founded his genus 

 Pherusa disagrees in almost every particular both with his 

 definition of the genus and of the subdivision in which he 

 placed it! 



Under these circumstances, and in accordance with no. 11 

 of Strickland's Rules for Zoological Nomenclature, adopted 

 by a strong committee of the British Association in 1865, it 

 seems clear that Pherusa fucicola. Leach, should be discarded 

 from our lists. In this rule it is laid down that " definition 

 is necessary before a zoological term can acquire any authority," 

 and that " Definition properly implies a distinct exposition of 

 essential characters, and in all cases we conceive this to be 

 indispensable." It is certain that Leach's description of 

 Piierusa does not comply with the above conditions. 



There appears, however, to be no reason why the genus 

 Pherusa as defined by Spence Bate in the Brit. Mus. Cat., 

 and which, as we have seen, is entirely distinct from Pherusa 

 of Leach, should not retain its place under the name of the 

 former author. 



Dismissing P. fucicola of Milne- Edwards and the figure of 

 Desmarest as of no value, being founded on the erroneous 

 figure in the 'Encycl. Britannica,' the synonymy of this species 

 will then stand as follows : — 



Genus Pherusa, Bate, 1862. 



Pherusa Jurinii, M.-Edvvards. 



Atnphitho'e Jurinei, M.-Edvvards, Ann. des Sciences Naturelles, 1830, 



vol. xx. p. 376. 

 Amphito'e Jurinii, M.-Edwards, Hist. Nat. des CrustactSes, iii. p. 30, 



pi. i. fig. 2 (1840). 

 Amphitho'e norvegica, Rathke, Acta Acadeinia Nat. Cur. Leopold. Carol. 



1843, vol. xx. p. 84, pi. iv. 

 Paramphitho'e norvegica, Bruzelius, Skand. Auipkip. Gamni. p. 77 



(1859). 

 Pherusa fucicola, Bate, Brit. Mus. Cat. Ampkipoda, p. 145, pi. xxvii. 



fig. 10 (1802). 

 Calliope norvegica. Bate, lk-it. Mus. Cat. Ainph. p. 150. 

 Calliopius norvegicus, Boeck, Skand. og Arkt. Amphipoder, p. 348, 



pi. xxii. fig. 6 (1876). 

 Pherusa fucicola, Carus, Prod. Faunae Mediterr. voL i. p. 404 (1885). 



It may be asked why I have not displaced Pherusa, Bate, 

 in favour of the older genus Paramphitho'e, Bruzelius. I reply 

 that PleusteSj Bate, 1858, is still older, and, as amended by 



Ann. & Mag. iV. Hist. Ser. 6. Vol. vii. 29 



