1914-] W. M. Tattersall : Crustacea Amphipoda. 451 



Telson (fig. 16) triangular in shape, about as broad as long, 

 slightly notched at the apex, a long and a short spine at the tip 

 of each lobe of the apex, a single rather strong spine somewhat 

 distal to the centre of each lateral margin. 



Length of an adult male and female, 9 mm. 



The determination of the generic position of this species has 

 been a matter of some difficult3V The fourth joint of the palp 

 of the maxilliped is distinctly present, but exceedingly small 

 and cannot be called anj^thing more than a vestige. The value 

 of the presence or absence of this joint in the classification of 

 the genera of the Talitridae has never been satisfactorily set 

 forth. Stebbing (1906) separates the genus Parorchestia from the 

 Orchestia group of genera on the ground that the fourth joint of 

 the palp of the maxilliped is " distinct though very small, conical 

 and having a spine on the truncate apex." In Orchestia the same 

 joint is described as an "obscure rudiment." Unfortunately 

 there does not seem to be any published figure of the maxilliped 

 palp of Parorchestia and, having no material of this genus at my 

 disposal, I have not been able to form an}'' opinion as to the 

 amount of difference implied in the above two descriptions. I 

 have, therefore, decided that in the present species the fourth 

 joint of the maxilliped palp is 'an obscure rudiment" and referred 

 it to the Orchestia group of genera. In this group, consisting of 

 Talitrus, Orchestoidea, Orchestia and Talorchestia, it seems to belong 

 to the last genus by the combination of the characters of the first 

 and second gnathopods in the two sexes, namely, first gnathopod 

 simple in the female, subchelate in the male, the second gnathopod 

 feebly chelate in the female, strongly' subchelate in the male. 

 But, among described species, T. kempii comes nearest to Orches- 

 tia parvispinosa which seems to me to be certainly congeneric with 

 the present form. This species was placed by its describer, Weber 

 (1892), in the genus Orchestia and both Stebbing (1906) and Chilton 

 (igi2), who examined specimens from the type localit}^ have 

 retained it in this genus. But the figures of the first gnathopod 

 of the female given by both Weber and Chilton, illustrate, in my 

 opinion, a limb which can only be described as simple and, there- 

 fore, of a form which would exclude the species from the genus 

 Orchestia. I propose, therefore, to transfer the species 0. parvis- 

 pinosa, Weber, to the genus Talorchestia and to include the 

 present species in the same genus. 



The problem is, however, still further complicated by the 

 form of the first and second gnathopods in the specimens which 

 I have called immature males (figs. 10 and 11). I do not know 

 what other interpretation can be placed on these specimens 

 though it is unfortunate that the sex of immature specimens of the 

 Talitridae is exceedingly difficult to determine, for want of an 

 external label in the form of copulatory organs. We know from 

 the researches of Barrois (1887) that the males of some species, at 

 any rate, of this group of Amphipoda, do not attain the full deve- 

 lopment of their gnathopoda till the final moults, up till which 



