PROTO. 37 



other, while the seventh pair are much nearer the sixth. 

 The fifth pair of legs are the shortest, the fourth pair 

 being longer, and the third still a little longer. The last 

 two pairs of legs are long and powerful. The branchiae 

 are attached to the second, third, and fourth pairs of 

 legs. The tail is rudimentary, and the appendages at- 

 tached to it almost obsolete. 



The geographical range of this genus is, as yet, 

 limited to the British seas and the adjacent coast, with 

 the exception of a single specimen taken by Dana on the 

 south-eastern shores of South America. 



Latreille appears to have made much confusion respect- 

 ing the nomenclature of the present group by attempting, 

 in his different works,* to distinguish his genus Leptomera 

 from that of Proto of Leach, proposing also a third 

 generic name Naupredia (Naupridia, Milne Edwards), for 

 an animal described as having only ten legs in a con- 

 tinuous series, those of the second, third, and fourth 

 pairs having a vesicle at the base, and which is evidently 

 a Proto with the sixth and seventh pairs of legs acci- 

 dentally broken off.f He has evidently, also, fallen into 

 error in giving the Gammarus pedatus of Montagu and 

 of Miiiler and the Squilla ventricosa of Miiller as three 

 distinct species, referable to separate sections or sub- 

 genera. 



* Regne Animal, 1st edit. iii. p. 51 ; 2nd edit. iv. pp. 127, 128. Nouv. 

 Diet. d'Hist. Nat. 2nd edit. p. 433 (Art. Chevrolle) ; xvii. p. 485 (Art. 

 Leptomere) ; xxviii. p. 177 (Art. Proton). 



f Van Beneden (Recherches sur la Faune litt. de Belgique, Crust. 1861, 

 p. 97, pi. xvii.) has described a species which he names Naupredia tristis, 

 asserting that it is a perfect animal, and not a mutilated Proto (Leptomera). 

 It is only five millemetres long, and is most probably in a very young state. 

 It entirely agrees with Proto, except in the inarticulated flagellum of the 

 antennae and want of the four hind legs. It is possible that these may 

 be subsequently developed ? 



