Cylindropsyllus brevicornis, &c. 135 
long as the preceding segment in the female. Anal oper- 
culum not prominent, and without spines. The furcal rami 
are twice as long as they are broad, with a large apical seta 
which is nearly one-third the length of the body. All the 
segments of the body are smooth, without spines, but there 
are groups of exceedingly minute cilia on the ventral side 
of the abdominal segments (Pl. V. fig. 1) and a pair of 
minute setz on the dorsal margin of each (PI. V. fig. 3). 
The first antenna (Pl. VI. fig. 1) of the female is short 
and consists of five joints, the first two being thicker than 
the remainder and forming a distinct basal part. The third 
and fourth joints are short, the fourth bearing a thick 
zsthete extending far beyond the end of the antenna, The 
distal joint is as long as the third and fourth combined, and 
armed at its apex with two sete and an esthete, the latter 
springing from the same base as one of the sete. In the 
male the antenna is not geniculated and appears to be com- 
posed of two joints only, since the two basal joints are fused, 
and the remaining joints are only partially distinct. Viewed 
from above, the last three joints appear completely fused, 
the long zsthete springing from the edge of a peculiar notch, 
which probably serves as a hook for grasping the female 
CPT VI. fies. 1), 12). 
The second antenna is the same in both sexes and consists 
of three joints (Pl. VI. figs. 2, 3). The second joint bears 
two small sete in place of the external ramus, which is 
absent. I have seen one specimen in which this joint, in 
both limbs, bore a long blunt-pointed seta (Pl. VI. fig. 3). 
The distal joint is armed with five or six strong claws and 
a pair of sete which spring from the same basis. One of 
these sete has a bifurcated tip, and in some specimens there 
appears to be a hyaline prolongation with a bead at the end 
similar to the esthetes of the antenne of Cladocera. 
The mouth-parts (text-fig. 1) consist, as in Cylindropsyllus, 
of three pairs of appendages only, the maxillipedes being 
absent. In C. levis there are a pair of minute triangular 
plates behind the second pair of maxille which, as Prof. 
Sars suggests, may represent the maxillipedes, but there is no 
trace of them in Horsiella. The mandible consists of a large 
quadrangular base and a slender chewing part with three or 
four blunt teeth, no trace of an external ramus being found. 
The first maxilla has a two-jointed palp and a single broad 
terminal lobe armed with three teeth and a few spines. 
The second maxilla is two-jointed, the basal part bearing, in 
place of the usual setigerous lobes, a single finger-like 
process with a comb of minute hook-like spines. The second 
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