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BRITISH ENTOMOSTRACA. 
the upper edge of the centre plate. The second pair 
(f. 2 e) is flat and stout, composed each of a body which is 
indistinctly divided into three segments. The anterior 
edge is prominently marked with several eminences, 
from each of which spring two rather long setae, directed 
towards the mouth. The posterior or third pair of foot- 
jaws (f. 2 /) is much larger than the preceding, and is 
formed of seven rings, the first two of which are large in 
proportion to the other five. 
The legs are five pairs in number, and the first four, as 
in the Cyclopidae, are double. The basal portion consists 
of two articulations. In the first pair (f. 2 g) the external 
branch consists of three joints, and the internal of two. 
In the three succeeding pairs (f. 2 h) each of the branches 
is composed of three segments, and all are furnished with 
plumose setae. The fifth pair is differently formed from 
the others, and is strong and well-developed compared 
with that of the Cyclopidae. They differ also from 
each other in the two sexes. Those of the male (f. 2 i) 
are almost cylindrical, and consist of two unequal branches 
arising from a common footstalk. The right branch is 
much the larger of the two, and is formed of three articu- 
lations, the last of which is terminated by a long and 
strong hook. The left has four rings, and is terminated 
by two short spines. This pair of legs is erroneously con- 
sidered by Jurine to be the sexual organs ; the shorter of 
the two branches containing, he believes, the organ itself. 
In the female (f. 2 j) the right branch is very much the 
larger of the two, and consists of three joints, the last of 
which is terminated by a strong curved claw. The left 
branch is very slender, composed of only one joint, and a 
terminal spine. These organs in the female are called, 
by Jurine, the “ fulcra, or supports of the external ovary.” 
The dorsal vessel, or heart, is very distinctly to be seen 
under the second and third segment of the body. It is 
oval, and gives origin to two vessels of equal size, one 
going to the head, and the other to the abdomen, and has 
another organ attached to it, which is called by Jurine 
