298 PHYLUM ARTHROPODA. 
When the-branchial chamber is opened the large pyramidal gills are 
seen, also the long sword-shaped epipodite (flabellum) of the first 
maxillipede which seems to help the “baler,” the smaller and mobile 
epipodites borne by the second and third maxillipedes, and the broad 
Fic. 152.— Ventral aspect of female shore crab. 
Aéd., Abdomen ; #x#., third maxillipede. 
scaphognathite of the second maxilla which bales the water forwards 
and outwards, 
It must be clearly understood that the branchial chamber is entirely 
outside of the body, being formed by the lateral extension of a hollow 
reduplicature from the tergal region. 
The large gizzard, the enormous greyish-yellow hepatopancreas, the 
transparent pericardium, and other organs are readily seen. 
SystEmaTIC SURVEY OF THE Ciass CRUSTACEA - 
(1) Entomostraca, lower forms. 
They are usually small and simple. 
The number of segments and ap- 
pendages is very diverse. 
The larva is generally hatched as a 
simple unsegmented Mauplius. 
There is no gastric mill. 
The excretory organ is associated 
with the second maxillz. 
(2) Malacostraca, higher forms. 
They are usually larger and more 
complex. 
The head consists of 5, the thorax. 
of 8, the abdomen of 6 (7 in 
Leptostraca) segments. 
The larva is usually higher than a 
Naupiius. 
There is often a gastric mill. 
The excretory organ is usually 
associated with the antennz, but 
maxillary glands may be present 
in the larvee, and may even per- 
sist in adults. 
