THE OSTRACODA 



793 



The first pair of maxillae (Fig. 1245 c) is formed of a thick, mus 

 cular, basal part, from the extremities of which four dij^iiifomi 

 processes originate. The larger of these prominences ( Fig. 1 ^45 c'l 

 is jointed and movable and must evidently be regarded a,s a palp 

 whereas the three remaining form the immediate continuation .)f 

 the basal part and are the true masticatory lobes. The first <jnc of 

 these is usually armed with two strong spines (Fig. 1 245 c^ and Fig. 

 1270 e) which may or may not be toothed, and are regarded as of 

 specific importance. To the outer side of the basal part a large 



Fig. 1245. (a) Lower lip or labium; {b) Mandible with palp; (c) First maiilU with braachbl pUta; 



{d) Second maxilla of female with palp {Cypris ifuonirtum). 



semilunar lamella (Fig. 1245 c^) is attached, which is generally called 

 the branchial plate. This plate may be seen to move rhythmically 

 in the living animal, and is for the purpose of renewing the sup|)ly 

 of fresh oxygen-laden water within the shell ca\ it >•. It is dircctwl 

 obliquely upwards and exhibits along the posterior edge a scries of 

 dense and regular finely plumose setae, from 16 to 20 in numlx-r. 



The second pair of maxillae (Fig. 1245^) consists of the same 

 principal parts as the first, though ditTerent in ai)pearance. Thr 

 basal part (Fig. 1245 d') is much smaller, not divided at the end. and 

 terminating in a single masticatory lobe. The branchial lamella 

 (Fig. 1245 d^) are usually semicircular and provided with a few plu- 

 mose setae, while the palps (Fig. 1245 (P and Fig. 1290 d- "-" -f 



