84 



C. CHILTON. 



Fig. 3. Talitrus syl- 

 vaticus, maxilliped. 



and I have been able to compare it with 

 specimens collected many years ago by 

 the late R. Helms near the top of Mount 

 Kosciusko, and find that it also agrees pre- 

 cisely with these specimens. The general 

 external appearance of these terrestrial 

 Amphipoda is very much the same in 

 species found in widely separated lands, 

 and it is not always easy to get definite 

 points of distinction that can be readily 

 examined. Sayce has pointed out that 

 the species in question is a genuine species 

 of Talitrus, since the gnathopoda of the 

 males and females are almost identical in 

 structure; it is thus clearly marked off from species of 

 Parorchestia, in which the males have the second gnatho- 

 poda developed into powerful subchelate organs. In species 

 of Parorchestia, however, the males are often very rare* 

 and the same thing may be the case with Talitrus, so that 

 it is not always easy to apply this sexual difference. In 

 the present case, fortunately, Talitrus sylvaticus can 

 apparently be pretty readily recognised by the three follow- 

 ing points: — 



(1) The first gnathopod. — In this, the side-plate distinctly 

 narrows distally, the carpus expands distally, is much 

 longer than the propod, and has on the under or posterior 

 side, a small sub-pellucid area marked off from the rest of 

 the joint by a fairly regular row of spinules ; the propod 

 narrows towards the dactyl, there is no appreciable palm,, 

 but the posterior margin is armed with spines of varying: 

 sizes, (see fig. 1). 



(2) The third peraeopod has the basal joint distinctly 

 narrowing distally, the posterior margin being irregularly 

 serrate and provided with a few spinules chiefly on the 

 lower part, (see fig. 2). 



