590 Wisconsin Academy of Sciences, Arts, and Letters. 
posteriorly, with a projection carrying the tail and toes; no true 
foot is present. The abdomen is flattend ventrally and has two 
longitudinal keels or lateral expansions, beginning at the anterior 
transverse fold and most prominent at about two thirds the length, 
where the cross section of the body is nearly semicircular; from 
this point it decreases in size and disappears at the base of the 
posterior projection. The rounded tail has dorsally a very large 
spur with a knob-like enlargement at the base and a conical point. 
The toes are fairly long, about one tenth of the total length, very 
robust, acutely pointed, and slightly curved; they are carried 
wide apart and appear to be incapable of any lateral motion. 
The dorsal and lateral antennae are small setigerous papillae 
in the normal positions. 
The corona extends down on the ventral side about one third 
the length of the body; the post-oral portion forms a fairly 
prominent chin. The auricles are very short and stout, and the 
ciliation is continuous with the corona. 
The mastax is virgate, and the trophi are highly asymmetric. 
The fulcrum is very long, slender, and tapering; the posterior 
end is slightly expanded and incurved. The rami are roughly 
triangular in ventral view and are bent at an approximately 
right angle at the extreme anterior point. Continuing the line 
of the fulcrum, the rami have near their base a blunt projection, 
bifid at the tip, which represents the basal apophysis of the 
malleate mastax; behind this projection the rami are slightly ex¬ 
cavate. The right ramus is minutely denticulate and finely 
striated; the left ramus has four blunt teeth on its inner margin. 
The alulae are very unequally developed; the right is of normal 
size, ending in an acute point, while the left is of huge propor¬ 
tions, very broad and strongly curved, and continuing backward 
until nearly opposite the mid-point of the fulcrum. The unci 
have a triangular basal plate; the left uncus has a large, strongly 
developed ventral tooth, which is clubbed at the point and has a 
fairly large pre-uncial tooth attached to its ventral edge; closely 
appressed to this is a slightly shorter and much more slender 
tooth, from the clubbed tip of which a diagonal rib crosses the 
basal plate to the external dorsal angle. The ventral tooth on the 
right ramus is slightly shorter than its mate on the opposite side; 
it is followed by two very slender teeth, and from the tip of the 
third tooth a diagonal rib crosses the basal plate to the external 
dorsal angle. The anterior half of the manubrium is a very 
