20 CRUSTACEA—BRANCHIOPODA CHAP. 
coiled proboscis of a butterfly, and the triangular membrane folded 
like a fan beside it, so that much of the organ is concealed, and 
the general appearance of the head is that shown in Fig. 5. 
During copulation, the whole structure is widely extended. 
The males of Artemia (Fig. 7) have the second antenna two- 
jointed, the basal joint bearing an inner tubercle, the terminal joint 
being flattened and 
bluntly pointed, its 
outer margin provided 
with a membranous 
outgrowth. In A. 
fertilis the breadth 
of the second joint 
varies greatly, the 
narrower forms  pre- 
senting a certain 
remote resemblance to 
Fic. 7.—Artemia fertilis. Front view oi the head of a Branchinecta. In the 
Fink Ree ans large second antennae, 4.2; males of. Polyartemia 
A.1, first ¢ ae, 
‘the second antennae 
have a remarkable branched form not easily comparable with 
that found in other Branchipodidae. 
The cephalic jaws are fairly uniform throughout the order. 
The mandibles have an undivided molar surface, and no palp ; 
the first maxilla is very generally a triangular plate, with a 
setose biting edge; mandibles and maxillae are covered by the 
labrum. The second maxilla generally lies outside the chamber 
formed by the labrum, and is a simple oval plate, with or 
without a special process for the duct of the kidney. 
The thoracic limbs, in front of the genital segments, are not 
as a rule differentiated into anterior maxillipedes and posterior 
locomotive appendages, as in higher forms; we have seen, 
however, that all these limbs take part in the prehension of food, 
and except in the Limnadiidae they all assist in locomotion. One 
of the middle thoracic legs of Artemia (Fig. 8, A) has a 
flattened stem, with seven processes on its inner, and two 
on its outer margin. The gnathobase (gn) is large, and 
fringed with long plumose setae, each of which is jointed ; this 
is followed by four smaller “ endites” (or processes on the median 
side), and then by two larger ones, the terminal endite (the sixth, 
