64 



Guide to Crustacea. 



Table-case 

 No. 1:^. 



Table- 

 cases Nos 



especially in mountain streams. In the family FoyccUanidac, the 

 short and broad carapace, without a prominent rostrum, and the 

 fact that the abdomen is folded under the body, give the animals 

 quite a crab-like appearance. They are, however, very closely 

 allied to the Galatheidae. All the species are found in shallow 

 water. The little " Porcelain Crabs " (Porcella)ia) of British coasts 

 are represented in tropical seas by numerous species, some of which, 

 like those exhibited, are of considerable size and striking colours. 



The small tribe Hippidea in- 

 cludes small, crab-like, burrowing 

 forms, living in sand and having 

 the feet flattened for digging. 

 They are only found in the warmer 

 seas. In one of the families of 

 this tribe, the Alhunoidac (Fig. 43), 

 when the animals are buried in 

 sand, respiration is carried on by 

 means of a tube formed by the 

 long antennules, each of which 

 bears a double row of stiff hairs. 

 It is noteworthy that in the Bra- 

 chyuran Corystidae {see Table-case 

 No. 15), which have a very similar 

 respiratory siphon, it is formed, 

 not, as in this case, by the 

 antennules, but by the antennae. 



Albiiin'a si/i)iiiisf(i (reduced). 

 Table-case No. 12.J 



Sub-Okder 3.— BKACHYURA. 



The Brachyura, or true 

 Crabs, are distinguished from the 

 other Decapoda by having the abdomen short and bent up under 

 the body. The " front " sends down a process to meet the 

 epistome, and thus forms a septum between the antennules. The 

 sixth pair of abdominal appendages (uropods) are generally absent, 

 rarely present as rudiments. I'he third pair of maxillipeds are 



pan- 



of 



)lding doors 



generally broad and flattened, forming 

 which cover the other mouth-parts. 



The Brachyura are usually divided into live Tribes, which, 

 however, are not all of equal value : — 



Tribe 1— Dromiacea. Tribe 3 — Oxyrhyueha. 



,, 2 Oxystomata. ,, 4 -Cyclometopa.. 



Tribe 5 -Calonietopa. 



