180 
BRITISH ENTOMOSTRACA. 
derable size ; the second is nearly equally large ; the third 
is short, about half the size of preceding ; and the fourth 
is more slender, but considerably larger than the third. 
The second is beset on both upper and lower edge with 
numerous stout setae, and from the junction of the third 
and fourth there issues two or three long, slender fila- 
ments ; while the last joint is terminated by several strong 
serrated spines. 
The natatory foot (t. XXII, f. 1 b) is a remarkable 
organ. It is composed of eight articulations. The 
first, or basilar joint, is very large, fleshy, and of a 
rounded oval form. The second joint is very narrow, com- 
pared with the first, and about one third of the length; 
while the remaining six are short, the whole scarcely 
equalling the second in length. From the base of each 
of these seven articulations issues a long filament, whilst 
from the anterior margin of the basilar joint there springs 
an appendage, consisting of two nearly equal, slender 
joints, the latter terminating in two blunt, crooked claws. 
The first pair of jaws consists each of a square-formed 
plate, furnished on the inferior edge with three or four 
finger-like appendages, each provided with several short, 
but stout setas, and having attached to its upper margin 
a large triangular- shaped plate, armed with about fifty fila- 
ments of considerable length. The second pair (t. XXII, 
f. 1 d , d) is composed each of a short, stout body of three 
articulations. The first joint is rather broad ; the second 
larger, and furnished on its lower edge with three rounded 
finger-like bodies, each of which sends off several short 
setae, while the third is very short and conical, and sends 
off about eight stout, somewhat serrated spines from its 
extremity and lower margin. 
The oviferous feet (t. XXII, f. 1 /) are organs of a very 
peculiar appearance and structure. They are long, cylin- 
drical, slender, and of a twisted form. They are each divided 
into very numerous short articulations, and armed at the 
free extremity with about eight or ten short, sharp-pointed 
spines, which again are in their turn provided with several 
