CRUSTACEA 
The Crustacea include Crabs, Lobsters, Crayfish, Barna- 
cles and many more allied forms, Tlie3' differ from the other 
Arthropoda (Insects, Millipedes and Centipedes, Spiders and 
Scorpions) chietly by breathing by means of gills instead of 
tracheae. The vast majority of them live ^n water; excep- 
tions are only the Land Crabs and Wood-lice. In typical cases 
they have two pairs of antennae. The name 'Crustacea' is due 
to their chitinous integument having become hard through ihe 
deposition of carbonate of lime. 
The classification of tlie Crustacea is in the first instance 
based upon the characters of the larval stages. To discuss 
these in a popular ' Guide,' would be too technical, nor can we 
attempt to examine the various orders which contain (mly 
species of minute size. We restrict ourselves to those groups 
the leading features of which are large enough to be studied 
with the naked eye. 
CRABS AND LOBSTERS (Decapoda), 
Crabs and Lobsters together form the order * Decapoda,' 
so called because they have five pairs of strongly developed 
limbs. However, their total number of appendages is much 
greater, most of the segments of the body ^generally nineteen) 
bearing appendages, like antennae, jaws and swimmerets. The 
Crabs are called ' Brachyura ' from their short tails, and the 
Lobsters ' Macrura ' from their long tails. 
One of the most conmion local crabs is Gonwsoma natator 
(see pi, XVIH, fig. 2). It can at any time be seen in the Fish 
Market The generic name is due to the body being drawn out 
into a sharp angle at either side. Closely allied is the much 
rarer Gomosouta crudfernnt which on its back shows a large and 
distinct cross, yellow upon olive-brown ground. A specimen of 
it was presented by Mr, C. H. Clarke in June last. — Most curi- 
ous is Podophihahmts vigil which name may be translated as the 
* Stalk-eyed Watchman,' lis eyes are placed on long movable 
stalks which are quite two inches in length. Specimens of it 
