CYPROIDEA.. 2979 



bular leg) appearing like an appendage to the mandible. The other 

 type, characterizing the oceanic species, has the mandibular leg like an 

 ordinary leg in form, the first or mandibular joint bearing the next at 

 or near its apex, and the second joint (first of the so-called palpus of 

 other species) often aiding by a denticulate process in the mandibular 

 function. The structure in Limulus is here represented, and the true 

 relation of the part called the palpus is well shown. In both types the 

 terminal portion of the leg is prominent, and acts like a leg, though 

 largest and stoutest in the second type. In the first type, the first 

 joint of the palpus (second of the organ) bears an accessory branch, 

 which is wanting in the second type. 



The number of joints in the organ, counting the mandible as the 

 first, is five in both types, as will be seen on Plate 90. 



The first pair of appendages following the mandibles, is in all the 

 Cyproidea a pair of maxillae. They consist of two to four joints, and 

 have in the fresh-water species a plate above the base ciliated with long 

 plumose seta?. This plate is kept in constant vibration, evidently to pro- 

 duce a current of water over the body, for the purpose of aeration. The 

 body of the organ fig. 1 d, 2 d, Plate 90, terminates in four or five linear 

 lobes ending in a brush of setae, the outer of which lobes is two-jointed 

 and articulated at base. These two joints are properly therefore the two 

 terminal joints of the maxilla; and the preceding part appears also 

 sometimes to consist of two joints, the second of the two bearing the 

 lobe next to the jointed one. The ciliated plate was not observed 

 distinctly in the marine species, and probably does not exist, although 

 a similar one is found attached to the following pair. 



The second pair varies much in character. In the marine species 

 it is furnished with a large plate at base, edged with long plumose 

 hairs; which plate is wanting in Cypris and Cy there; and besides 

 this plate and the setigerous maxillary joint to which it belongs, 

 there is also at times a slender three-jointed appendage ending in one 

 or two long setae. In Cypris, on the contrary, the organ has a maxil- 

 lary process interiorly, and a lateral or posterior one-jointed branch, 

 with few short setae at apex. In Cy there, these organs are represented 

 by a pair of slender five-jointed legs, ending in a long slender claw, 

 similar to the two following pairs. 



The third pair is a proper leg in each of the genera, excepting 

 Cypridina. In Cypris and Cythere it is long and slender ; in Con- 

 choecia and Halocypris it is shorter, and has a few setae at apex ; in 





