70 Guide to Crustacea. 



Table-case and a female are mounted alDOve the Wall-cases at the south end 

 No. 14. Qf ^i^g Gallery. They were coloured after a drawing of a live 

 specimen by a Japanese artist. 



In the family Parthenopidae, the chelipeds are usually much 

 more massive than the other legs, and the orbits are well 

 formed. The typical members of this family have taken to the 

 same habitat as the Oxystomata, burying themselves in sand or 

 shingle, and they show many superficial resemblances in the 

 shape of the chelipeds, the lateral extensions of the carapace, and 

 the disposition of the Ijreathing channels, to such Oxystomes 

 as Calappa. In many species, as in the Partlicnopc horrida 

 exhibited, the carapace and limbs are remarkably rugged and 

 luieven. 

 Table-case The Crabs belonging to the Tribe Cyclometopa have the 

 No. 15. carapace, as a rule, broader than long, wuth the antero- 

 lateral borders strongly curved, and the postero-lateral 

 borders convergent ; the front is not produced into a ros- 

 trum ; the mouth-frame is square ; the genital ducts of the 

 male open on the bases of the last pair of legs. Witli the 

 exception of the Eiver-crabs, all the members of this tribe inhabit 

 the sea. 



In the large and very varied family Xanthidae, the carapace, 

 as a rule, is transversely oval, and its surface is often lobulated. 

 The species of this family ai'e very abundant, especially in the 

 tropics, in the littoral region. Three species of Xcnitlw are 

 British, one of which, X. incisiis, is exhibited. The vivid 

 colours of some tropical species are exemplified by the painted 

 specimens of Carpilius maciUatus and Zozymus acneus. To this 

 family also belongs the large Tasmanian Crab, Pseiidocarcinus 

 gigas, a specimen of which is mounted above Wall-cases Nos. 5 

 and 6. 



A specimen of Zo.zijiiiti>i acneus is exhibited which has been 

 prepared to illustrate the disposition of the branchial passages in 

 Cyclometopa, for comparison wath similar preparations of the 

 Oxystomata in Table-case No. 18. The third maxilliped has been 

 removed on one side to show the quadrilatei'al shape of the 

 mouth-frame (coloured red), characteristic of most Brachyura. 

 The arrow indicates the course of the respiratory current, which, 

 however, may sometimes be temporarily reversed, especially in 

 burrowing species. 



The tj'pical memi)ers of the family J'orltniidac (Swimming 

 Crabs) may be reeognisetl by the fliittened, paddle-shaped, last 



