84 ZOOLOGISCHE MEDEDEELINGEN — DEEL II. 



joints, and especially by the conspicuous, curved projection at the base 

 of the inferior margin of the hand of the second gnathopod in the adult 

 male, whereas the palm margin itself is oblique, almost straight and 

 spineless (see Delia Valle 1. c. pi. 15 f. 28). 



Though I made a careful search among all our specimens of Talitrus 

 saltator (Montagu) I have not succeeded in finding one single specimen, 

 which answered to Stebbing's description of the female of T. brito. 

 Neither in the shape of the joints of the antennular peduncle, nor 

 in the number of joints in the flagellum of the upper 'antennae there 

 is any marked difference between the female of Talorchestia brito and 

 that of Talitrus saltator. Comparing Stebbing's figure of the first gna- 

 thopod of the female of his species and that of Sars (Crustacea of Nor- 

 way, v. I, Amphipoda, 1895, pi. 9) of the same gnathopod of the female 

 of Talitrus saltator, we may only find this difference, that the second 

 joint in the first named species is very broad, twice as long as broad, 

 whereas in the latter species it is three times as long as broad. Stebbing 

 remarks, that the hind margin of this gnathopod is „fringed with stout, 

 round-headed spines ; the subterminal hair in these and many of the 

 other spines is so thick, that it produces the appearance of a cleft head 

 to the spine", but this very feature is present in females of true Talitrus 

 saltator in exactly the same way. In the carpopodite (wrist) of the second 

 gnathopod there is a remarkable difference between the two species: in 

 Talorchestia brito it is much inflated, broadest in the distal half, and the 

 hind margin is regularly curved and strongly convex (as in Orchestia 

 gammarellus) ; in Talitrus saltator it is much more slender, with the 

 greatest width before the middle, the hind margin is feebly concave or 

 straight in its distal half. Among about 40 specimens of the latter species, 

 collected at Katwijk, I always found, without exception, this latter feature. 

 Of course I do not deny the existence of true females of Talorchestia 

 brito, but it will be extremely difficult to distinguish these from the 

 same sex of Talitrus saltator. The hand of the second gnathopod of the 

 females does not afford any particular feature which may be used in 

 separating the two species. 



When alive, there seems to be a rather marked difference. According 

 to G. 0. Sars (1. c. p. 23) the colour of Talitrus saltator (called by him 

 T. locusta) is „light greyish-white, with dark bluish markings on the 

 back", that of Talorchestia brito is „yellowish-white, here and there barred 

 with deeper yellow, bordered along the side-plates and across the head 

 with a beautiful purple, bands of which also sometimes extend across 

 the back of the pleon" (Stebbing, p. 327). The habitat of these two 

 species is also somewhat different, as the latter species „occupies a zone 



