356 Messrs. T. and A. Scott on some 
edge is nearly straight and provided with a few small and 
equidistant fascicles of minute hairs; the outer margin is 
gently curved, densely setose on the upper half and with 
several setee on the lower half and apex (Pl. XVI. fig. 6). 
Caudal stylets short, scarcely equal in length to the last 
abdominal segment. 
Male. The male is similar to the female except in the 
following particulars :—The antennules, which are moderately 
stout, are modified for grasping (Pl. XV. fig. 12). The 
second pair of swimming-feet are very similar to those of the 
male of Thalestris harpactoides, Claus, except that the second 
and third joints of the inner branches are coalescent (Pl. XVI. 
fig. 5). In the fifth pair the basal joint is much shorter than 
in the female, being scarcely produced interiorly ; it bears 
three moderately stout apical sete, the middle one of which 
is about twice the length of the others; the secondary joint 
is somewhat similar to that of the female fifth pair, and is 
furnished with six stout spiniform sete, three on the outer 
margin and three at the apex (Pl. XVI. fig. 7). 
Habitat. Firth of Forth; collected April 1895. 
Remarks. Thalestris peltata (Boeck) is not very unlike 
Zaus spinatus in general appearance ; moreover, in the struc- 
ture of some of its appendages, and especially of the first pair 
of swimming-feet, it resembles certain species of Dactylopus. 
The chief points of difference between Vhalestris and Dacty- 
lopus seem to be these—in Thalestris the outer and inner 
branches of the first pair of swimming-feet are usually of equal 
length, or the outer may be slightly longer than the inner, and 
the middle joint of the outer branches is usually considerably 
longer than the first or third joints, whereas in Dactylopus 
the outer branches are usually shorter than the inner branches, 
and the middle joint of the outer branches usually equal in 
length to, or only slightly longer than, the first or third joints. 
But in Vhalestris peltata and Dactylopus tisboides the two 
genera approach somewhat closely to each other. The 
description and figures of this species in Dr. Brady’s ‘ Mono- 
graph of British Copepoda’ agree very well with our 
observations, except that he describes the secondary branch 
of the antenne as three-jointed. He had only one specimen 
to describe from; and as we have obtained both males and 
females, we thought that a set of drawings showing their 
sexual differences might be of interest. We did not observe 
the eyes mentioned by Boeck. 
