370 CRUSTACEA ENTOMOSTRACA. 



here, that the simple condition of these appendages in the Branchiopods 

 is a specialized and not a primitive character. The small size and simple 

 character of the maxillae is perhaps dependent on the peculiar habit of 

 members of this genus, alluded to below, of passing the food forwards 

 along the ventral groove. 



The postcephalic appendages (legs or feet) are usually very 

 numerous in the Branchiopoda Phyllopoda, and are smaller to- 

 wards the posterior end of the body. In this division of the order 

 they consist, as its name implies, of flattened leaf-like appendages 

 which act as swimming feet, and by the eddies they set up in 

 the water assist in procuring food. They are set transversely on 

 either side of the ventral middle line, and the inner and outer mar- 

 gins are produced into endites and exites. In the mid-ventral 

 line of the body, between the closely ranked legs of either side 

 there is a deep groove, limited at the sides by the endites, 

 and closed above by the sterna of the body segments. Along 

 this groove the material containing the food is, in most if not all 

 Branchiopods, passed forward to the mouth, assisted on its way 

 by the movements of the appendages. It can thus be acted 

 on by the opposed endites of the latter, set on either side. 

 The basal endites, and especially the first or " coxal " endite, 

 have accordingly the character of masticatory lobes, being short, 

 firm and beset with coarse setae. 



There are usually six endites on a leg (Fig. 249) ; those near 

 the base directed inward, and those situated distally directed 

 more and more in the line of the axis' of the leg, so that the 

 most distal form terminal lobes. 



The exites are two or three in number. The most distal of 

 them, having in several cases a triangular shape, is known as 

 the ftabellum. The proximal exite or exites (2 in Poly- 

 artemia and Chirocephalus) are generally simple lobes, devoid 

 of setae.* A respiratory function has been especially attributed 

 to them, but, as the justice of this is disputable, the term bracts 

 may be conveniently retained for them. 



It is not at all obvious how the short multilobed thoracic legs 

 of the Branchiopoda conform to the biramous type of limb so 

 widely found among the Crustacea ; and, as a fact, now one 

 and now another pair of the terminal lobes has been regarded 



* In cases where two are present they appear to belong to the two 

 proximal divisions of the protopodite. 



