124 Wisconsin Academy of Sciences, Arts, and Letters. 
Mandible :—This appendage, PL X, fig. 3, is. strong, the 
chi tin of the basal part being very thick, especially along the 
dorsal and ventral walls. Dors ally the base projects backward 
forming a heavy blunt spur. The basal part (that back of the 
insertion of the palp) contains two' muscles originating, one 
above and one below, at the proximal end and passing forward 
to be inserted, in the same relative position, on the base of the 
palp. Beyond the point of attachment of the palp, the man¬ 
dible becomes much smaller, is. slightly curved, and ends in six 
pairs of masticatory teeth. These are heavy, branched and in 
part hollow; all are slightly curved, the upper and lower pairs 
more so than the others. Between the teeth are small bristles 
not at. all prominent and much smaller 1 than any of those fig¬ 
ured by Claus (3). Xear the end of the mandible is a single 
seta, differing from all others in being unsegmented and termi¬ 
nating in a short rod. The palp is four 1 segmented and bears 
setae at the distal end of the following segments; second, one 
seta; third and fourth, each two setae. These are all similar 
in structure to the setae of the antennae. The palp terminates 
in a claw which towards the end is abruptly curved. A large 
muscle passes from the base of the palp to the base of the ter¬ 
minal claw, and a second smaller muscle of doubtful origin is 
inserted dorsally on the proximal end of the last segment. 
The branchial plate ^reduced exopod, Claus) differs from all 
those figured by Claus (3) in being very small and short, and 
bearing but. three filaments. Each filament consists! of a. large 
basal segment followed by numerous small ones. 
Maxilla :—The elongated basal part of the maxilla, PL X, 
fig. 4 (protopodit) bears on its outer surface near the base, the 
gill-plate. Along the outer margin of this plate are thirteen 
branchial filaments of the usual form. Between the insertion 
of the gill-plate and of the palp the chitinous covering becomes 
very much thickened to form, a supporting framework, the up¬ 
per and lower parts of which are connected on either side by 
two oblique bands. At its tip the maxilla becomes much nar¬ 
rower ending in two slightly curved setae. 
The palp arises just anterior to the two chitinous bands and 
extends a, little beyond the end of the maxilla. It is un- 
