418 Mr. A. 0. Walker on Pherusa fucicola (Leach), 



XLIV. — On Pherusa fucicola (Leach). 

 By Alfred O. Walker. 



The confusion that has arisen about this species is so great 

 that it appears worth while to make an effort towards clearing 

 it up. It was first described by Leach in 1814 in the ' Edin- 

 burgh Encyclopaedia,' vol. vii., art. Crustaceology, and in the 

 Trans. Linn. Soc. vol. xi. part 2, 1815, p. 360. 'in the latter 

 he describes the genus Pherusa as follows : — " Antennae 

 superiores seta nulla ad articuli quarti basin. Cauda superne 

 haud fasciculato-spinosa. Manus filiforines." The only 

 species, P. fucicola, is described as follows : — " P. testaceo- 

 cinerea aut griseo-cinerea rubro-varia. Habitat inter fucos in 

 Danmoniae australis mari rarius." The definition of the 

 genus only differs from that of Amphithoe (as pointed out by 

 Stebbingin his invaluable ' Challenger' Bibliography) in the 

 substitution of " manus filiformes " for " manus ovatae." 



In the 'Encyclopaedia Britannica,' 1816, Supp. pi. xxi. 

 Pherusa fucicola is figured. The first gnathopods are very 

 slender, while the second are much longer, the wrist and hand 

 together forming an elongated oval, of which the wrist 

 occupies more than one third the length. It cannot be said 

 that this figure agrees with Leach's definition of the genus 

 (" manus filiformes ") or of the Subdivision II. in which he 

 places it, the definition of which is " Pedum paria duo antica in 

 utroque sexu monodactyla conformia" Only one other 

 Amphipod is figured, viz. Melita pahnata, Montagu. This 

 has no secondary appendage to the upper antennae and no 

 finger on the hand of the second gnathopod. These figures 

 therefore are of little or no scientific value. 



Desmarest (' Considerations sur la Classe des Crustacees,' 

 p. 268, pi. xlv. fig. 10) translates Leach's description and 

 gives a figure which appears to be an indifferent copy of that 

 in the Encycl. Brit., the hand of the second gnathopod being 

 again large and ovate. 



Milne-Edwards (Hist. Nat. des Crustacees, 1840, vol. iii. 

 p. 32) says that Amphithoe fucicola, Leach, is distinguished 

 by the great inequality between the first two pair of feet, the 

 first pair being filiform and the second, though much thicker 

 (" plus grosses "), being still slender (" greles ") and elon- 

 gated. This description seems to be founded on the figure in 

 the Encycl. Brit, and not on Leach's description. Milne- 

 Edwards does not appear to have seen the species. 



In 1857 Costa (< Amfipodi del Regno di Napoli,' p. 209, 

 pi. iii. fig. 2) described Amphithoe micrura, adding that it 



