5*20 History of British Entomostraca. 
tennse are, but yet he does not mention the long filaments which they 
possess, and by which their action, as fins, is principally produ- 
ced. They are considered by Latreille as acting, along with the an- 
tennae, as respiratory organs. The second pair of feet (Fig. I.f. Fig. 
4,) are not so strong as the first pair, and are composed of five articu- 
lations also, the last of which is terminated by one strong curved 
hook. The first pair are directed backwards ; the second are direct- 
ed forwards ; they want the long filaments which the first pair pos- 
sess, and are thus only used for walking with. The third pair (Fig. 
1. g. Fig. 5,) arise immediately behind the second pair, and consist 
of four articulations ;* the last of which is terminated by two short 
hooks, and has a filament thrown back from its extremity, like a 
spur. They are curved upwards and backwards, and are always 
contained within the shell, never being extruded. Their use, ac- 
cording to Straus, is to support the ovaries. Jurine considers them 
as somehow connected with the matrix, but says he is ignorant of 
their use; the figure which he gives of them is very incorrect. 
Mouth The mouth is situate in the inferior surface of the ante- 
rior lobe of the body, and consists of a lip, a kind of sternum,t per- 
forming the functions of an inferior lip ; a pair of palpiferous man- 
dibles, and two pairs of jaws. The lip, (Fig. 6, .,) says Straus, is 
composed of a great scaly piece like a hood, forming a projection 
which advances between the two anterior feet, and is fixed to tjie 
body by four long apophyses. The sternum, or lower lip > (Fig. 6. 
b.) according to the same author, is elongated, triangular, and move- 
able, articulates with the lip, and has at its extremity two curved 
apophyses to articulate it with second pair of jaws. The mandible 
(Fig. 7- g- Fig. 1. 7z,) is very large, and is formed^of two pieces. The 
larger, or mandible, properly so called, (Fig. 7- a,) is terminated at 
superior extremity by a point, and at the lower or incisive extremity 
by five pretty strong teeth. The other piece is in the form of a re- 
gular palpus, (Fig. 7, 6.) which issues^from about the middle length 
of the proper mandible, and consists of three joints, provided with 
several setae, the first of which joints has, near its base, a very small 
branchial plate, (Fig. 7 c,) terminated by five digitations. This 
palpus is the second pair of feet of Jurine, the " barbillon," of 
Muller, the use of which, both agree, is to cause a current of water 
towards the mouth, carrying with it the particles destined for the 
insect's food. The first pair of jaws (Fig. 1. t. Fig. 8,) have for their 
base a large square-shaped plate, (Fig. 8. ,) furnished at anterior 
* Straus says five. f Straus. 
