64 
Guide to Crustacea. 
Table-case 
No. 12. 
Table- 
cases Nos. 
12-16. 
especially in mountain streams. In the family Porcellanidae, 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 ” ( Porcellanct ) 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 Albuneidae (Pig. 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- 
cliyuran 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. 
Sub-Order 3. — BBACHYURA. 
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. The third pair of maxillipeds are 
generally broad and flattened, forming a pair of “folding doors” 
which cover the other mouth-parts. 
The Brachyura are usually divided into five Tribes, which, 
however, are not all of equal value : — 
Tribe 1- Dromiacea. Tribe 3 — Oxyrhyncha. 
,, 2- Oxystomata. ,, 4 — Cyclometopa. 
Tribe 5— Catometopa. 
Fig. 43. 
Albunea symnista (reduced). 
[Table-case No. 12.] 
