History of British Entomostraca. 521 
extremity with four fingers, the superior of which is of two joiuts, 
the other three of only one, but all terminated by several long hairs . 
From the external edge of this plate, forming the base, arises a 
large elongated branchial plate, (Fig. 8. 6,) which gives off from the 
superior crescentic shaped edge, a row of nineteen long spines, ar- 
ranged like the teeth of a comb. The square plate with its fingers 
must be Jurine's third pair of feet, though if so, the figure which 
this author gives of these organs, as well as of his second pair of 
feet, (the palpi of the mandible, of Straus,) is decidedly incorrect. 
He seems to have been ignorant of the existence of the branchial 
plate, as he asks, " if it be true that the branchiae be the first cha- 
racter in the Crustacea, where shall we place them in these mono- 
culi ? in the antennae, feet, or tail ? we cannot give a preference to 
any one of these parts over another."* The second pair of jaws 
(Fig. 9) are much smaller, and are articulated on the posterior angle 
of sternum by means of the two curved apophyses at its extremity. 
Each jaw consists of two flattened joints, the latter of which has 
several stiff hairs at extremity, and on external edge gives off a 
rounded finger, which Straus says, he thinks, must be considered 
as a palpus. The posterior portion of the body is terminated by a 
long tail, (Fig. 1. A. Fig. 10,) consisting of two lengthened stalks, each 
terminated by two short curved stylets, with a third implanted on 
upper edge, a little above them. This tail is free, and possesses 
much freedom of motion, the insect extruding it from the shell at 
pleasure. One great use of it seems to be to clean the interior 
part of the shell, which its length and mobility fit it well for ; but 
Straus says also that its use is perhaps to serve for depositing the 
eggs. The anatomy of the internal parts of the body is more diffi- 
cult to make out distinctly. The alimentary canal, according to 
Straus, consists of a short narrow oesophagus, a large oblong sto- 
mach, occupying the whole of the dorsal region of the body ; and a 
simple intestine nearly as large as the stomach, becoming narrower 
towards the posterior extremity, and opening by an anus between 
the two stylets which form the tail. The ovaries are two large 
simple, conical vessels, placed externally upon the posterior portion 
of the body, and open one at the side of the other into the anterior 
part of extremity of abdomen, where they communicate with 
the canal formed by the tail. There is another organ, the use of 
which is not so well ascertained. It is a large and conical mass, 
situated above the articulation of the mandibles, of a granulated 
* Histoire des Monocles, &c. 
