of the Fishery Board for Scotland. 75 
may only be a somewhat abnormal variety of the more common P. bicolor. 
This form has scarcely any trace of the brown colouration so conspicuous 
in P. bicolor ; it is also rather broader in proportion to the length. The 
second dorsal plate is as wide as the posterior part of the cephalic shield, 
and the posterior margins of each of the two lobes is obliquely truncated 
instead of being rounded as in the normal form. The lobes of the next 
plate, which have their posterior margins somewhat evenly rounded, are 
separated by a semicircular hollow and are not spread so widely apart as 
in the normal P. bicolor. The anal lamina are also more prominent than 
in the normal form. Till further specimens of this pale-coloured form 
are obtained, I prefer to regard it as only an accidental variety of P. bicolor. 
Genus Hatschekia, Poche (1902). 
(syn. Clavella, Oken, nec. Cuvier). 
Hatschekia cornigera, sp. n. Pl. IIL., figs. 1-7. 
I found this Copepod moderately frequent on the gills of several 
specimens of Sea Bream, Pagellus centrodontus, De la Roche, sent to the 
Laboratory from the Fish Market at Aberdeen. The species, however, does 
not appear to be generally common, for a considerable proportion of the 
fishes examined had their gills apparently free from the parasites. 
Hatschekia cornigera is a small species, and measures only about 2:4 
millimeters in length exclusive of the ovisacs, which are moderately 
elongated. It is, like some other species of the same genus, of a narrow 
elongated form (fig. |), but may be distinguished from them by the 
cephalon being produced backwards in the form of a short blunt-pointed, 
spur-like process on the median dorsal aspect, as in the drawing (fig. 2), 
which shows a profile view of the head and part of the thorax. 
The antennules are short, stout, and five-jointed, and sparingly setiferous, 
the third and last joints being shorter than the others (fig. 3). 
The antenne are small, but being armed with stout terminal hooked 
spines they form effective grasping organs (fig. 4). 
The mandibles, maxille, and maxillipeds do not appear to differ greatly 
from the corresponding appendages of other members of the genus. 
Figure 5 represents one of the second pair of maxillipeds ; they are each 
three-jointed, moderately elongated, and armed with a stout terminal 
claw which is bifurcated at the extremity ; the second joint bears also a 
small curved spine near its proximal end; there is also a small seta at the 
base of the términal claw. 
The thoracic limbs comprise apparently only two pairs, as in other 
members of the genus. Both pairs are somewhat alike in structure, but 
the first are considerably smaller than the second pair. One of the first 
pair is represented by figure 6; it consists of a moderately stc ut, two-jointed 
basal part and two, two-jointed branches. The inner branch is rather 
shorter than the outer, and the first joint is shorter than the end one; in 
the outer branch the joints are nearly of equal length. Both branches are 
furnished with several stout spines. In the second pair, one of which is 
represented by figure 7, the inner branches are stouter and rather longer 
than the outer, and the end joint is about twice the length of the first. In 
the outer branch the end joint is the smallest. Both branches are 
furnished with a few terminal spines, one cf which is considerably stouter 
and rather more elongate than the others. 
The colour of the parasites resembles that of the gills of the fish. 
