Cylindropsyllus brevicornis, &c. 139 
is much dilated and deeply notched. The second antenna is 
three-jointed, the third joint bearing six strong spines and a 
single long spine-like seta (Pl. VII. fig. 1). The external 
ramus is reduced to a small knob bearing a single seta, 
The mouth-parts are as in D. fairliensis, consisting of man- 
dibles, two pairs of maxilla, and a pair of maxillipedes. 
The mandible bears a one-jointed palp with two setz (Pl. VII. 
fig. 2). The maxillipedes are well developed and appear to 
agree with those of D. fairliensis, as figured by Prof. Sars. 
The swimming-legs are almost the same in both sexes, 
and are less slender than in D. fairliensis. In the first pair 
(Pl. VII. fig. 3) the second basal joint bears a strong spine 
on its inner angle, which is absent from the succeeding legs. 
In the male (Pl. VII. fig. 4) this spine is curved and slightly 
_ barbed. The internal rami of all legs are two-jointed, 
nearly as long as the external branch, but they differ some- 
what in the different legs in respect of the sete borne by 
them. The internal rami of the third and fourth pairs of 
legs of the male differ from those of the female in having 
the inner spine of the second joint considerably longer, and 
in having a long spine springing from the middle of the 
first joint of the fourth leg in space of a short apical spine. 
The fifth pair of legs are the same in both sexes, con- 
sisting of small knobs bearing each a small lateral seta and 
three terminal sete of which the middle one is very small 
(Pl. VII. fig. 12). 
Length. Female 1:15 and 1:3 mm.; male 1:2 and 1°45 mm. 
The specimens described above form part of the Norman 
Collection in the British Museum (Natural History), and 
are labelled “‘ Cylindropsyllus levis, E. Loch Tarbert, Loch 
Fyne, 1886, T. Scott.” (B.M. nos. 45248-252). I have to 
express my thanks to Dr. W. T. Calman and the authorities 
of the Museum for allowing me to examine them. 
The species differs from D. fairliensis in the form of the 
furcal rami of the female, in the structure of the antenne, 
and in certain details of the length and arrangement of the 
setz of the swimming-legs. 
EXPLANATION OF THE PLATES. 
PLATE V. 
Horsiella brevicornis (Van Douwe), 
Fig. 1. Female, ventral view. 
Fig. 2. Male, dorsal view. 
Fig. 3. Male, lateral view. 
