26 



CRUSTACEA BRANCHIOPODA 



Fig. 7. — Artemia fertilis. Front view of the head of 

 male, showing the large second antennae, .4.2 

 A.\, first antennae. 



coiled proboscis of a butterfly, and the triaiigidar 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, tlie 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 

 Brancliinecta. In the 

 males of Polyartemia 

 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 

 labruin. 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 cjenital seianents, 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. 



