ORDER ISOPODA. 
221 
In these the impressed lines, or transverse sutures of the 
anterior segment of the tail, reach its lateral edges and divide 
it. The first articulation of the upper antennae forms an 
elongated palette, square or linear. 
The leaflets of the fins are usually narrower and more thick 
than in the preceding. The exterior one sometimes emboxes 
the other. The latter is prismatic. Their point of union 
presents the appearance of a knot or articulation. 
Sometimes the sixth segment of the body is sensibly of 
greater breadth than the preceding and the following. One 
of the two leaflets of the fins alone is projecting. 
JNLesa, Campecopea , Leach. 
Sometimes the sixth segment is of the length of the preced- 
ing and the following. (. Ncesa bidentata , Desm.) 
CiLiCiEA, Leach , 
In which one of the leaflets of the fins alone is projecting, 
the other being laid back against the posterior edge of the last 
segment. ( Cilicaa , Latreillii , Desm.) 
Cymodocea, Leach , 
In .which the two leaflets of the fins are projecting, and 
equally directed backwards. The sixth segment is not pro- 
longed posteriorly, and the last presents but a small lamina in 
an emargination. 
Dynamene, Leach , 
Like cymodocea in the projection and direction of the leaflets 
of the fins, but the sixth segment is prolonged behind, and 
the last presents but a simple cleft, without lamina. 
The others, such as 
