384 CRUSTACEA ENTOMOSTRACA. 



or absent altogether (G. W. Miiller). In these (Fig. 253, 3) 

 the appendages resemble legs, and end with strong hooked 

 bristles, by help of whi?h the animal can attach itself to sur- 

 rounding objects. 



In the region of the mouth, beneath and to the side of a toler- 

 ably large upper lip, there are two mandibles usually with a 

 broad and strongly toothed biting edge. In one division of the 

 Ostracods the Myodocopa the mandibles have the form of 

 legs rather than jaws. In the Cypridinidae even the masticatory 

 process on the basal joint may disappear, or be represented 

 by a small setose lobe (Fig. 254), while the palp has the form 

 of a strong leg. In the other division, the Podocopa, the palp 

 though still pediform has more moderate proportions, and 

 may be biramous (Fig. 253, -5). In exceptional cases (Paradoxo- 

 stoma), the mandibles are styliform and are enclosed in a 

 suctorial proboscis formed from the upper and under lips. 



The appendages which follow the mandibles are very vari- 

 ously modified in the different families of Ostracods in relation 

 to the function of mastication, or to locomotion or to both 

 combined. The fourth pair, or first maxillae, are jaws in all 

 except the small family Polycopidae, where they have the form 

 of short legs carrying a distinct outer ramus. In the Podocopa 

 they carry a large comb-like setose plate which by its move- 

 ment promotes the process of respiration, though it does not 

 itself act as a gill (Fig. 253, 6). The second maxillae (fifth pair) are 

 jaw-like in the Cypridinidae and carry an enormous respiratory 

 plate (Fig. 254). In the Halocypridae and Cypridae they have 

 an intermediate character between jaws and locomotory limbs, 

 the basal joint being stout and carrying a respiratory fan (small 

 in Cypris), and the endopodite forming a jointed appendage 

 directed backwards from it and provided with stiff claw-like 

 setae. In the Cytheridae the whole appendage is more slender 

 and leg-like. In the Polycopidae, where this is the last pair 

 of appendages, they are short and leg-like, and carry a respi- 

 ratory fan. 



The appendages of the sixth pair are again jaw-like in the 

 Cypridinidae, in the Cypridae and Cytheridae they are leg-like, 

 while in the Halocypridae they have an intermediate character. 

 The seventh pair are leg-like in the Cypridae and Cytheridae. In 

 the former family they occupy a peculiar position (Fig. 253, 9), 



