30 BRITISH FOSSILS. 



Neither antennules nor antennae are chelate or sub-chelate in 

 either sex. 



The mandible (fig. 3") consists of a basal joint and a palpiform 

 appendage. The outer half of the former is quadrate, convex 

 inferiorly, and presents, posteriorly and externally, a curved 

 articular process ; the middle of the basal joint is a little con- 

 stricted and flattened, while its internal portion widens again, and 

 ends in a truncated, toothed edge. The teeth are continuous with 

 the blade of the mandible, not articulated with it. The palp 

 springs from an excavated surface on the anterior and superior 

 face of the quadrate outer division. Its proximal joint is short 

 and rounded. The next is the longest, and as broad as or broader 

 than the basal joint, and wider distally than proximally. At the 

 distal end it supports two branches, the outer of which is 

 obscurely five-jointed ; the inner two-jointed. The toothed and 

 cutting extremities of the basal joints of the mandibles pass 

 between the labrum and the metastoma, and bite against one 

 another in the middle line. Those of the maxillae lie behind the 

 metastoma. The first maxilla (fig. 4) is nearly of the same size as the 

 mandible. Its basal joint is produced internally into a large curved 

 process, whose inner edge is beset with strong articulated setae, 

 which might almost be called elongated teeth, were they not setose 

 along their edges. Succeeding this articulation is a broad joint 

 produced internally into a narrow, transversely elongated, flattened 

 process, terminated by elongated setigerous setae externally, into a 

 broad flat plate bearing eight or ten extremely long and strong seti- 

 gerous setae ; five other obscurely marked joints follow these two. 



The next appendage (fig. 5) is not quite so long as that just 

 described; it is obscurely divided into seven joints and tapers 

 to its extremity, which, like its inner edge, is provided with very 

 long and strong setae. The inner setae are by far the stronger, 

 and are directed forwards so as nearly to reach the mouth. 



The fourth post-oral appendage (fig. 6) is more than twice as 

 long as the third. It consists of a short and strong, subcylindrical, 

 basal joint, beset along its inner margin with a row of very long 

 setigerous setse, and having a rounded projecting inner distal 

 angle. One long and five short gradually diminishing articulations 

 follow this. 



To this appendage succeed the five pairs of swimming feet (fig. 7), 

 of which the first and the last are smaller than the intermediate 

 ones. Each natatory limb consists of a stem (protopodite) and two 



